You searched for subject:(Large eddy simulation).
Showing records 1 – 30 of
577 total matches.
◁ [1] [2] [3] [4] [5] … [20] ▶
University of Notre Dame
1.
Anne L Tufts.
Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>.
Degree: Aerospace and Mechanical Engineering, 2018, University of Notre Dame
URL: https://curate.nd.edu/show/d217qn62j1g 
► Large-eddy simulation of a turbulent shear layer interacting with a thin airfoil is performed to investigate the sound generation. The turbulent shear layer is…
(more)
▼ Large-
eddy simulation of a turbulent shear
layer interacting with a thin airfoil is performed to investigate
the sound generation. The turbulent shear layer is generated using
a separate temporal
simulation and fed into airfoil simulations as
an inflow boundary condition to closely match the setup of a
previous experiment. Three different airfoil locations are
considered, one at the center of the shear layer and two in the
outer regions of the layer on both the high- and low-speed
sides.
Simulation results show that the impact of
the airfoil on the shear layer flow statistics is largest at the
center position and nearly negligible at the two outer positions.
The airfoil unsteady lift shows strong influence of the shear-layer
roller structures at all positions in addition to localized
small-scale fluctuations. The far-field sound is calculated using a
boundary-element solution to the Lighthill equation. Contributions
from sources in the airfoil leading and trailing edge regions are
evaluated and compared. Results show good agreement with
experimental spectra of leading edge noise over a wide frequency
range. The high and middle airfoils produce comparable sound
pressure levels, while the low airfoil produces the weakest sound.
Leading-edge interaction with the shear layer is shown to be the
dominant noise source at most frequencies, and self noise due to
trailing-edge vortex shedding is significant only for middle and
high airfoil positions at high
frequencies Pressure fluctuations on the airfoil
surface are also examined to elucidate the scattered-noise
production. At all airfoil positions, the spectral levels of the
spanwise-averaged surface pressure are largest at low frequencies
near the leading edge. Near the trailing edge of both the center
and high airfoils an increase in high-frequency spectral levels is
observed, confirming important trailing-edge contribution to the
high-frequency radiated sound.
Advisors/Committee Members: Flint Thomas, Committee Member, Meng Wang, Research Director, Scott Morris, Committee Member, Aleksandar Jemcov, Committee Member.
Subjects/Keywords: Aeroacoustics; Large-Eddy Simulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Tufts, A. L. (2018). Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>. (Thesis). University of Notre Dame. Retrieved from https://curate.nd.edu/show/d217qn62j1g
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Tufts, Anne L. “Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>.” 2018. Thesis, University of Notre Dame. Accessed February 27, 2021.
https://curate.nd.edu/show/d217qn62j1g.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Tufts, Anne L. “Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>.” 2018. Web. 27 Feb 2021.
Vancouver:
Tufts AL. Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>. [Internet] [Thesis]. University of Notre Dame; 2018. [cited 2021 Feb 27].
Available from: https://curate.nd.edu/show/d217qn62j1g.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Tufts AL. Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>. [Thesis]. University of Notre Dame; 2018. Available from: https://curate.nd.edu/show/d217qn62j1g
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Georgia Tech
2.
Li, Yixing.
High-fidelity numerical simulation and emulation of bi-fluid swirl injector flow and combustion dynamics.
Degree: PhD, Aerospace Engineering, 2019, Georgia Tech
URL: http://hdl.handle.net/1853/61698
► Injectors are critical components of combustion devices in liquid-fueled propulsion systems. By controlling the atomization and mixing of propellants, injectors can affect combustion efficiency, dynamic…
(more)
▼ Injectors are critical components of combustion devices in liquid-fueled propulsion systems. By controlling the atomization and mixing of propellants, injectors can affect combustion efficiency, dynamic characteristics, and engine life cycle. This work conducts a comprehensive study of the gas-centered liquid-swirl coaxial (GCLSC) injectors, operating at supercritical conditions. The study is composed of two parts. The first part investigates flow and combustion dynamics of GCLSC injectors based on high-fidelity
large eddy simulations (LES), and the second part presents a high-fidelity emulation framework for the prediction of spatiotemporally evovling flow and combustion in a significantly shorter turnaround time. For the first part of the study, LES simulations are conducted to study supercritical fluid flow dynamics and combustion characteristics of GCLSC injectors. Gaseous oxygen is axially injected into the center post at a temperature of 687.7K, while kerosene is tangentially introduced into the coaxial annulus at a temperature of 492.2K. The operating pressure is 25.3 MPa, well above the thermodynamic critical points of the propellants involved. Based on LES results, For non-reacting flows, detailed flow physics and structures are identified, followed by comprehensive analyses of mechanisms controlling key dynamic characteristics. These mechanisms include vortex shedding near the fuel injection slit, the shear layer instability in the recess region, and vortical expansion and merging in the taper region. For reacting flows, the flow field is categorized into four regions: propellant injection, flame initialization, flame development, and intensive combustion. Detailed flow structures and the flame evolution in each region are elaborated in detail. Moreover, the effects of the recess length on mixing, flow dynamics and combustion dynamics are investigated. The second part presents a high-fidelity data-driven emulation framework, which utilizes training data from LES and enables flow field emulation in reasonable turnaround time. The framework employs common kernel-smoothed proper orthogonal decomposition (CKSPOD) as the surrogate model, which is able to extract dominant coherent flow structures through hadamard-based POD and kriging, and reconstruct them to predict the flow field of a new case. Significant improvements, including common grid interpolation and physics-based conditions, are incorporated to this framework to accommodate the prediction of complicated mixing and combustion dynamics. In the current study, CKSPOD utilizes LES results of GCLSC injectors as training data, and recess length is chosen as the varying design parameter. Detailed evaluations of the predicted flow fields are carried out, and the current framework is able to capture both instantaneous and time-averaged flow fields with high accuracy. Moreover, the improved CKSPOD presents uncertainty quantification (UQ) of the predicted flow field, providing a metric for model fit. The proposed framework is further extended to injector design…
Advisors/Committee Members: Yang, Vigor (advisor), Lieuwen, Timothy (committee member), Sankar, Lakshmi (committee member), Oefelein, Joseph (committee member), Wu, Jeff (committee member), Wang, Xingjian (committee member).
Subjects/Keywords: Large Eddy simulation; Emulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Li, Y. (2019). High-fidelity numerical simulation and emulation of bi-fluid swirl injector flow and combustion dynamics. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/61698
Chicago Manual of Style (16th Edition):
Li, Yixing. “High-fidelity numerical simulation and emulation of bi-fluid swirl injector flow and combustion dynamics.” 2019. Doctoral Dissertation, Georgia Tech. Accessed February 27, 2021.
http://hdl.handle.net/1853/61698.
MLA Handbook (7th Edition):
Li, Yixing. “High-fidelity numerical simulation and emulation of bi-fluid swirl injector flow and combustion dynamics.” 2019. Web. 27 Feb 2021.
Vancouver:
Li Y. High-fidelity numerical simulation and emulation of bi-fluid swirl injector flow and combustion dynamics. [Internet] [Doctoral dissertation]. Georgia Tech; 2019. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/1853/61698.
Council of Science Editors:
Li Y. High-fidelity numerical simulation and emulation of bi-fluid swirl injector flow and combustion dynamics. [Doctoral Dissertation]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/61698
Universitat Politècnica de València
3.
Mompó Laborda, Juan Manuel.
Engineering Large Eddy Simulation of Diesel Sprays
.
Degree: 2014, Universitat Politècnica de València
URL: http://hdl.handle.net/10251/37345
► The main objective of this PhD thesis is the study of Diesel sprays under evaporative conditions by means of Large Eddy Simulations (LES) techniques. This…
(more)
▼ The main objective of this PhD thesis is the study of Diesel sprays under
evaporative conditions by means of
Large Eddy Simulations (LES) techniques.
This study has been performed implementing a precise, low-demanding LES
model in the free, full-purpose Computational Fluid Dynamics (CFD) code
OpenFOAM.
The starting point was a careful and exhaustive review of the physical processes
involved in sprays. An emphasis in CFD methodology, particularly for
LES methods, was essential for the thesis, as we were able to find the possible
problems and limitations of our approximation. Moreover, as the most
widely used techniques for the industrial
simulation of sprays are based on
the Reynolds-Averaged Navier-Stokes models, we have highlighted the many
advantages of LES modeling. As the latter are, by definition, more computationally
expensive than RANS, we made an optimal configuration that, while
it is able to recover accurately the experimental results, its characteristic time
is in the same order of magnitude that RANS ones. As applicability is a must
in this thesis, we use the surname ¿Engineering¿ LES.
One of the key points of the thesis has been the correct configuration of
the flow turbulent conditions on the inlet. In order to get accurate results,
the turbulent structures coming from this inlet need to be time- and spacecoherent.
An adequate calibration of this conditions is needed to perform any
spray
simulation.
Last but not least, all the simulations performed where validated against
experiments, obtaining a very good agreement even close to the nozzle
Advisors/Committee Members: Hoyas Calvo, Sergio (advisor).
Subjects/Keywords: Large Eddy Simulation;
Engineering;
Large;
Eddy;
Simulation;
LES;
Spray;
Diesel;
CFD;
Dynamic Structure;
Numerical simulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Mompó Laborda, J. M. (2014). Engineering Large Eddy Simulation of Diesel Sprays
. (Doctoral Dissertation). Universitat Politècnica de València. Retrieved from http://hdl.handle.net/10251/37345
Chicago Manual of Style (16th Edition):
Mompó Laborda, Juan Manuel. “Engineering Large Eddy Simulation of Diesel Sprays
.” 2014. Doctoral Dissertation, Universitat Politècnica de València. Accessed February 27, 2021.
http://hdl.handle.net/10251/37345.
MLA Handbook (7th Edition):
Mompó Laborda, Juan Manuel. “Engineering Large Eddy Simulation of Diesel Sprays
.” 2014. Web. 27 Feb 2021.
Vancouver:
Mompó Laborda JM. Engineering Large Eddy Simulation of Diesel Sprays
. [Internet] [Doctoral dissertation]. Universitat Politècnica de València; 2014. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/10251/37345.
Council of Science Editors:
Mompó Laborda JM. Engineering Large Eddy Simulation of Diesel Sprays
. [Doctoral Dissertation]. Universitat Politècnica de València; 2014. Available from: http://hdl.handle.net/10251/37345
Georgia Tech
4.
Dzanic, Tarik.
Investigation of ODE-based non-equilibrium wall shear stress models for large eddy simulation.
Degree: MS, Aerospace Engineering, 2019, Georgia Tech
URL: http://hdl.handle.net/1853/62711
► For high Reynolds number flows, wall modeling is essential for performing large eddy simulation at a reasonable computational cost. In this work, a novel low-cost…
(more)
▼ For high Reynolds number flows, wall modeling is essential for performing
large eddy simulation at a reasonable computational cost. In this work, a novel low-cost ODE-based non-equilibrium wall model is introduced for wall shear stress modeling in LES. Using polynomial approximations of the pressure gradient and convective terms obtained from interpolation of the LES solution, as opposed to direct evaluation of these gradients within the wall model, the governing wall model equations reduce from coupled PDEs to uncoupled ODEs that do not require an embedded wall model grid within the LES grid. Additionally, the steady form of the wall model equations was utilized, feasible due to the spatial decoupling of the wall model equations, and the effects of the temporal evolution on the wall shear stress were modeled. The effects of polynomial degree on the accuracy of the wall shear stress predictions were explored, and an empirical lag model was built to model the unsteady effects without requiring the solution of a time-stepping problem. Wall resolved
large eddy simulations of separated flow around the NASA wall mounted hump and an iced NACA 63A213 airfoil were performed and used as a reference for the comparison of the non-equilibrium wall model to a commonly used equilibrium wall model. The proposed non-equilibrium wall model was able to predict separated flow and laminar flow regions in much better agreement with the wall resolved results than the equilibrium wall model. Underpredictions in the skin friction coefficient in non-equilibrium flow regimes were reduced from 20-50% to less than 10% between the equilibrium and the non-equilibrium wall modeled approaches. Minor improvements in the pressure coefficient predictions were observed with the non-equilibrium model in the separated flow region of the iced airfoil. The results suggest that the proposed wall model can offer better predictions of separated and/or laminar flows compared to equilibrium wall models with negligible computational cost increase.
Advisors/Committee Members: Oefelein, Joseph (advisor), Menon, Suresh (advisor), Yeung, P. K. (advisor).
Subjects/Keywords: Large eddy simulation; Wall model; Non-equilibrium
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Dzanic, T. (2019). Investigation of ODE-based non-equilibrium wall shear stress models for large eddy simulation. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62711
Chicago Manual of Style (16th Edition):
Dzanic, Tarik. “Investigation of ODE-based non-equilibrium wall shear stress models for large eddy simulation.” 2019. Masters Thesis, Georgia Tech. Accessed February 27, 2021.
http://hdl.handle.net/1853/62711.
MLA Handbook (7th Edition):
Dzanic, Tarik. “Investigation of ODE-based non-equilibrium wall shear stress models for large eddy simulation.” 2019. Web. 27 Feb 2021.
Vancouver:
Dzanic T. Investigation of ODE-based non-equilibrium wall shear stress models for large eddy simulation. [Internet] [Masters thesis]. Georgia Tech; 2019. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/1853/62711.
Council of Science Editors:
Dzanic T. Investigation of ODE-based non-equilibrium wall shear stress models for large eddy simulation. [Masters Thesis]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/62711
University of Saskatchewan
5.
Moazamigoodarzi, Nader 1982-.
LARGE EDDY SIMULATION OF THE FLOW AROUND A FINITE SQUARE PRISM MOUNTED ON A GROUND PLANE.
Degree: 2018, University of Saskatchewan
URL: http://hdl.handle.net/10388/8939
► Dynamic subgrid-scale models for large eddy simulation (LES) offer the promise of being able to dynamically calibrate the residual stress field to the local flow…
(more)
▼ Dynamic subgrid-scale models for
large eddy simulation (LES) offer the promise of being able to dynamically calibrate the residual stress field to the local flow conditions. The first part of thesis reports on the application of two different dynamic subgrid-scale (SGS) models to predict the turbulent wake of a finite-height square prism mounted vertically on a ground plane. The prism aspect ratio was AR = 3, and the Reynolds number, based on the prism width and freestream velocity, was Re = 500. The approach flow was laminar with a thin boundary layer; the thickness at the location of the prism was approximately 0.2D. The flow over the top of the prism interacts with the flow along the ground plane and the vertical shear layers from the sidewalls to create a complicated wake structure. Both a linear dynamic Smagorinsky model (DSM) and dynamic nonlinear model (DNM) were implemented and tested for their ability to resolve the complex wake structure. Investigation of the dissipation of turbulence kinetic energy reveals that the DSM has a much larger SGS dissipation, whereas the DNM has a greater resolved-scale dissipation. The backscatter associated with the DSM is much more pervasive than that predicted by the DNM, which accounts for the numerical instability of the DSM. Overall, specific differences are observed in the wake predicted by the two SGS models, including some features of the mean velocity field.
The second part of the thesis explores the phase-averaged structure of the wake based on the prediction of the DNM. Phase-averaging based on the Strouhal number reveals a wake structure with quasi-periodic features that is much different from the mean vorticity field, which is characterised by two pairs of counter-rotating streamwise vortex tubes. The phase-averaged near-wake structure is dominated by vertical vortex cores formed by the shear layers being shed from the two sides of the prism. These tubes re-orient and interact as they detach from the prism and move downstream, giving evidence of the half-loop structures documented in previous studies. Each half-loop consists of a short vertical core near the ground plane, and a connector strand that tilts back upstream toward the prism. The shedding process is almost symmetric just downstream of the prism, but develops an asymmetric pattern farther downstream, characterised by the alternate development of half-loop structures on opposite sides of the wake. Further downstream in the wake, the phase-averaged flow is dominated by approximately streamwise vortex tubes associated with the connector strands.
Advisors/Committee Members: Bergstrom, Donald, Wiens, Travis, Sumner, David, Zhang, Chris, Evitts, Richard.
Subjects/Keywords: LARGE EDDY SIMULATION; FINITE SQUARE PRISM
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Moazamigoodarzi, N. 1. (2018). LARGE EDDY SIMULATION OF THE FLOW AROUND A FINITE SQUARE PRISM MOUNTED ON A GROUND PLANE. (Thesis). University of Saskatchewan. Retrieved from http://hdl.handle.net/10388/8939
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Moazamigoodarzi, Nader 1982-. “LARGE EDDY SIMULATION OF THE FLOW AROUND A FINITE SQUARE PRISM MOUNTED ON A GROUND PLANE.” 2018. Thesis, University of Saskatchewan. Accessed February 27, 2021.
http://hdl.handle.net/10388/8939.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Moazamigoodarzi, Nader 1982-. “LARGE EDDY SIMULATION OF THE FLOW AROUND A FINITE SQUARE PRISM MOUNTED ON A GROUND PLANE.” 2018. Web. 27 Feb 2021.
Vancouver:
Moazamigoodarzi N1. LARGE EDDY SIMULATION OF THE FLOW AROUND A FINITE SQUARE PRISM MOUNTED ON A GROUND PLANE. [Internet] [Thesis]. University of Saskatchewan; 2018. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/10388/8939.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Moazamigoodarzi N1. LARGE EDDY SIMULATION OF THE FLOW AROUND A FINITE SQUARE PRISM MOUNTED ON A GROUND PLANE. [Thesis]. University of Saskatchewan; 2018. Available from: http://hdl.handle.net/10388/8939
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Cambridge
6.
Wilsby, Oscar.
Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number.
Degree: PhD, 2019, University of Cambridge
URL: https://www.repository.cam.ac.uk/handle/1810/294622
► This thesis is an investigation into the production and prediction of broadband noise in axial compressors operating at low Reynolds number. The low Reynolds number…
(more)
▼ This thesis is an investigation into the production and prediction of broadband noise in axial compressors operating at low Reynolds number. The low Reynolds number (chord based ReC ≤ 5 × 104) regime presents new flow physics by the large regions of laminar flow that are present in the compressor. As such it is unclear how our conventional understanding of the noise sources in turbomachinery can be applied to this new regime.
The research was conducted by designing and constructing a new single stage rotor-stator compressor on which the subsequent research was based. The work utilized a combination of experimental, computational and analytical methods. Aerodynamic and acoustic properties were measured on the compressor installed in a duct with clean inflow over a wide range of operating points. These results were then used to validate a set of incompressible, wall resolved Large Eddy Simulations (LES) on operating points representing on and off-design behavior. In the existing literature, there have been few if any studies utilizing wall resolved LES of a 3D rotor blade geometry for aeroacoustic source evaluation. A mesh dependency study was conducted in order to assess the level of refinement needed for convergence of turbulent statistics. It was found that although a fine resolution was needed for convergence of velocity and pressure spectra describing acoustic sources, a relatively coarse LES could still provide similar estimates of second order statistics such as Reynolds stresses. When compared to experiment, the LES results show a pleasing ability to accurately capture both first and second order statistics as well as turbulent velocity spectra, which cannot be said about steady Reynolds Averaged Navier Stokes (RANS) simulations. The simulations reveal that a significant portion of the midspan region of the blade remains laminar for the entire blade chord up until the trailing edge. Spanwise migration of the flow due to the rotational forces allow the boundary layer to stay laminar and attached. Generation of turbulence is then mainly limited to the secondary flows at the hub and tip gap which account for a large proportion of the wake turbulence. The secondary flows also feed turbulence into the blade profile boundary layers in these regions.
A hybrid aeroacoustic prediction framework, based on the turbulent source description provided by the LES, and analytical acoustic propagation models are used to predict the overall sound power spectrum and compared favorably with the duct measurements. It is found that trailing edge noise and rotor-stator interaction noise are equally important contributors to the overall noise spectrum. However key narrowband humps which are not explained by these noise models exist, particularly off design.
Subjects/Keywords: Large eddy simulation; low reynolds number; aeroacoustics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wilsby, O. (2019). Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number. (Doctoral Dissertation). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/294622
Chicago Manual of Style (16th Edition):
Wilsby, Oscar. “Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number.” 2019. Doctoral Dissertation, University of Cambridge. Accessed February 27, 2021.
https://www.repository.cam.ac.uk/handle/1810/294622.
MLA Handbook (7th Edition):
Wilsby, Oscar. “Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number.” 2019. Web. 27 Feb 2021.
Vancouver:
Wilsby O. Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number. [Internet] [Doctoral dissertation]. University of Cambridge; 2019. [cited 2021 Feb 27].
Available from: https://www.repository.cam.ac.uk/handle/1810/294622.
Council of Science Editors:
Wilsby O. Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number. [Doctoral Dissertation]. University of Cambridge; 2019. Available from: https://www.repository.cam.ac.uk/handle/1810/294622
University of Cambridge
7.
Denby, Leif Christopher.
Using high-resolution modelling to improve the parameterisation of convection in a climate model.
Degree: PhD, 2017, University of Cambridge
URL: https://www.repository.cam.ac.uk/handle/1810/269850
► In this work high-resolution numerical simulation (Large-Eddie Simulation, LES) has been used to study the characteristic factors causing and influencing the development of moist convective…
(more)
▼ In this work high-resolution numerical simulation (Large-Eddie Simulation, LES) has been used to study the characteristic factors causing and influencing the development of moist convective clouds. Through this work a 1D cloud-model was derived from first principles to represent the vertical profile of individual convective clouds. A microphysics framework was implemented to ensure identical behaviour in LES and cloud-model integration where the microphysical processes represented are numerically integrated using a novel adaptive step microphysics integration which uses the physical speed at which a process takes place to adjust the integration step size (in space and time). This work also introduces a simple representation of cloud-droplet formation which allows for super-saturation to exist in-cloud and through this provide more physical representation of the in-cloud state.
Together with high-resolution simulation of isolated individual and interacting multiple clouds in environmental conditions leading to shallow convection, the 1D cloud-model was used to infer that the principal influence on moist convective clouds is the entrainment of air from a cloud’s immediate environment which is significantly different from the environmental mean state. This suggests that convection parameterisations must represent the influence of moist convective downdrafts to properly predict the vertical structure of convective clouds so as to correctly predict the cloud-top height and vertical transport. Finally it was found that cloud-base radius is not in itself adequate as a means of classification for defining cloud-types as clouds with the same cloud-base radius showed large variation (≈ 600m) in cloud-top height. Based on simulations of individual convective clouds it was found that 3D simulations are necessary to capture the full dynamic behaviour of convective clouds (2D axisymmetric simulations have too little entrainment) and that agreement with the 1D cloud-model could only be found when entrainment was diagnosed from simulation instead of being parameterised by the traditional Morton-Turner model and only for 2D axisymmetric simulations, suggesting that the 1D cloud-model will require further extension or the diagnosis of entrainment improved.
Subjects/Keywords: convective clouds; large-eddy simulation; cloud entrainment
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Denby, L. C. (2017). Using high-resolution modelling to improve the parameterisation of convection in a climate model. (Doctoral Dissertation). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/269850
Chicago Manual of Style (16th Edition):
Denby, Leif Christopher. “Using high-resolution modelling to improve the parameterisation of convection in a climate model.” 2017. Doctoral Dissertation, University of Cambridge. Accessed February 27, 2021.
https://www.repository.cam.ac.uk/handle/1810/269850.
MLA Handbook (7th Edition):
Denby, Leif Christopher. “Using high-resolution modelling to improve the parameterisation of convection in a climate model.” 2017. Web. 27 Feb 2021.
Vancouver:
Denby LC. Using high-resolution modelling to improve the parameterisation of convection in a climate model. [Internet] [Doctoral dissertation]. University of Cambridge; 2017. [cited 2021 Feb 27].
Available from: https://www.repository.cam.ac.uk/handle/1810/269850.
Council of Science Editors:
Denby LC. Using high-resolution modelling to improve the parameterisation of convection in a climate model. [Doctoral Dissertation]. University of Cambridge; 2017. Available from: https://www.repository.cam.ac.uk/handle/1810/269850
University of Cambridge
8.
Wilsby, Oscar.
Broadband noise prediction of an axial compressor operating at low Reynolds number.
Degree: PhD, 2019, University of Cambridge
URL: https://doi.org/10.17863/CAM.41726
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782948
► This thesis is an investigation into the production and prediction of broadband noise in axial compressors operating at low Reynolds number. The low Reynolds number…
(more)
▼ This thesis is an investigation into the production and prediction of broadband noise in axial compressors operating at low Reynolds number. The low Reynolds number (chord based ReC ≤ 5 × 104) regime presents new flow physics by the large regions of laminar flow that are present in the compressor. As such it is unclear how our conventional understanding of the noise sources in turbomachinery can be applied to this new regime. The research was conducted by designing and constructing a new single stage rotor-stator compressor on which the subsequent research was based. The work utilized a combination of experimental, computational and analytical methods. Aerodynamic and acoustic properties were measured on the compressor installed in a duct with clean inflow over a wide range of operating points. These results were then used to validate a set of incompressible, wall resolved Large Eddy Simulations (LES) on operating points representing on and off-design behavior. In the existing literature, there have been few if any studies utilizing wall resolved LES of a 3D rotor blade geometry for aeroacoustic source evaluation. A mesh dependency study was conducted in order to assess the level of refinement needed for convergence of turbulent statistics. It was found that although a fine resolution was needed for convergence of velocity and pressure spectra describing acoustic sources, a relatively coarse LES could still provide similar estimates of second order statistics such as Reynolds stresses. When compared to experiment, the LES results show a pleasing ability to accurately capture both first and second order statistics as well as turbulent velocity spectra, which cannot be said about steady Reynolds Averaged Navier Stokes (RANS) simulations. The simulations reveal that a significant portion of the midspan region of the blade remains laminar for the entire blade chord up until the trailing edge. Spanwise migration of the flow due to the rotational forces allow the boundary layer to stay laminar and attached. Generation of turbulence is then mainly limited to the secondary flows at the hub and tip gap which account for a large proportion of the wake turbulence. The secondary flows also feed turbulence into the blade profile boundary layers in these regions. A hybrid aeroacoustic prediction framework, based on the turbulent source description provided by the LES, and analytical acoustic propagation models are used to predict the overall sound power spectrum and compared favorably with the duct measurements. It is found that trailing edge noise and rotor-stator interaction noise are equally important contributors to the overall noise spectrum. However key narrowband humps which are not explained by these noise models exist, particularly off design.
Subjects/Keywords: Large eddy simulation; low reynolds number; aeroacoustics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wilsby, O. (2019). Broadband noise prediction of an axial compressor operating at low Reynolds number. (Doctoral Dissertation). University of Cambridge. Retrieved from https://doi.org/10.17863/CAM.41726 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782948
Chicago Manual of Style (16th Edition):
Wilsby, Oscar. “Broadband noise prediction of an axial compressor operating at low Reynolds number.” 2019. Doctoral Dissertation, University of Cambridge. Accessed February 27, 2021.
https://doi.org/10.17863/CAM.41726 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782948.
MLA Handbook (7th Edition):
Wilsby, Oscar. “Broadband noise prediction of an axial compressor operating at low Reynolds number.” 2019. Web. 27 Feb 2021.
Vancouver:
Wilsby O. Broadband noise prediction of an axial compressor operating at low Reynolds number. [Internet] [Doctoral dissertation]. University of Cambridge; 2019. [cited 2021 Feb 27].
Available from: https://doi.org/10.17863/CAM.41726 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782948.
Council of Science Editors:
Wilsby O. Broadband noise prediction of an axial compressor operating at low Reynolds number. [Doctoral Dissertation]. University of Cambridge; 2019. Available from: https://doi.org/10.17863/CAM.41726 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782948
Oklahoma State University
9.
Maulik, Romit.
Data-driven sub-grid model development for large eddy simulations of turbulence.
Degree: Mechanical and Aerospace Engineering, 2019, Oklahoma State University
URL: http://hdl.handle.net/11244/323826
► Turbulence modeling remains an active area of research due to its significant impact on a diverse set of challenges such as those pertaining to the…
(more)
▼ Turbulence modeling remains an active area of research due to its significant impact on a diverse set of challenges such as those pertaining to the aerospace and geophysical communities. Researchers continue to search for modeling strategies that improve the representation of high-wavenumber content in practical computational fluid dynamics applications. The recent successes of machine learning in the physical sciences have motivated a number of studies into the modeling of turbulence from a data-driven point of view. In this research, we utilize physics-informed machine learning to reconstruct the effect of unresolved frequencies (i.e., small-scale turbulence) on grid-resolved flow-variables obtained through
large eddy simulation. In general, it is seen that the successful development of any data-driven strategy relies on two phases - learning and a-posteriori deployment. The former requires the synthesis of labeled data from direct numerical simulations of our target phenomenon whereas the latter requires the development of stability preserving modifications instead of a direct deployment of learning predictions. These stability preserving techniques may be through prediction modulation - where learning outputs are deployed via an intermediate statistical truncation. They may also be through the utilization of model classifiers where the traditional L
2-minimization strategy is avoided for a categorical cross-entropy error which flags for the most stable model deployment at a point on the computational grid. In this thesis, we outline several investigations utilizing the aforementioned philosophies and come to the conclusion that sub-grid turbulence models built through the utilization of machine learning are capable of recovering viable statistical trends in stabilized a-posteriori deployments for Kraichnan and Kolmogorov turbulence. Therefore, they represent a promising tool for the generation of closures that may be utilized in flows that belong to different configurations and have different sub-grid modeling requirements.
Advisors/Committee Members: San, Omer (advisor), Jayaraman, Balaji (committee member), Santhanakrishnan, Arvind (committee member), Ku, Ja Eun (committee member).
Subjects/Keywords: large eddy simulation; machine learning; turbulence modeling
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Maulik, R. (2019). Data-driven sub-grid model development for large eddy simulations of turbulence. (Thesis). Oklahoma State University. Retrieved from http://hdl.handle.net/11244/323826
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Maulik, Romit. “Data-driven sub-grid model development for large eddy simulations of turbulence.” 2019. Thesis, Oklahoma State University. Accessed February 27, 2021.
http://hdl.handle.net/11244/323826.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Maulik, Romit. “Data-driven sub-grid model development for large eddy simulations of turbulence.” 2019. Web. 27 Feb 2021.
Vancouver:
Maulik R. Data-driven sub-grid model development for large eddy simulations of turbulence. [Internet] [Thesis]. Oklahoma State University; 2019. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/11244/323826.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Maulik R. Data-driven sub-grid model development for large eddy simulations of turbulence. [Thesis]. Oklahoma State University; 2019. Available from: http://hdl.handle.net/11244/323826
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Virginia Tech
10.
Patil, Sunil.
Large Eddy Simulations of high Reynolds number Complex Flows with Synthetic Inlet Turbulence.
Degree: PhD, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/26060
► The research was motivated by the desire to use Large Eddy Simulations (LES) to calculate liner heat transfer in industrial scale gas turbine combustors, which…
(more)
▼ The research was motivated by the desire to use
Large Eddy Simulations (LES) to calculate liner heat transfer in industrial scale gas turbine combustors, which operate at high Reynolds numbers and high Swirl numbers. LES has several challenges which need to be surmounted for general application to complex high Reynolds number turbulent flows. The primary challenge in wall bounded flows is the need for very fine grids in the vicinity of walls, which makes LES impractical at high Reynolds numbers. An additional challenge is the accurate representation of inlet turbulent conditions for developing flows such that the computational domain size is limited to the immediate region of interest. The generalization of solutions to surmount these issues in complex geometries and grids is yet another challenge.
To meet these challenges, a novel formulation, implementation, and validation of a two layer velocity and temperature zonal wall model along with the implementation of the synthetic
eddy method in a generalized coordinate system LES framework is presented in this thesis. The wall model greatly alleviates the grid requirements, whereas the synthetic
eddy method provides accurate turbulent inlet boundary conditions. The methods are validated in turbulent channel flow up to a Reynolds number of 2x106, a backward facing step at Re=40,000, before application to a model swirl combustor at Re=20,000 with a Swirl number of 0.43 and flow and heat transfer in an industrial scale can combustor at Re=80,000 and Swirl number of 0.7. The integrated zonal near wall approach for velocity and temperature is then successfully used to investigate flow and heat transfer in a statistically three-dimensional flow of a ribbed duct passage used for the internal cooling of turbine blades. The zonal wall model is further modified to take in to account the effects of surface roughness and successfully used to investigate flow in a rod roughened channel at high Reynolds numbers up to 60,000.
In all cases it is shown that the zonal wall model used with the synthetic
eddy method for inlet turbulence generation can result in
large savings in computational cost without any significant loss in accuracy when compared to wall resolved LES and experiments. In a turbulent channel flow at Re=45,000, computational complexity was reduced by a factor of 285 using wall modeled LES, whereas in a statistically three-dimensional flow and heat transfer in a ribbed duct, at Re=20,000, the computational complexity was reduced by a factor between 60 and 140. In a swirl dominated can combustor at Re=20,000, the reduction was more modest at a factor of 9.
Advisors/Committee Members: Tafti, Danesh K. (committeechair), Simpson, Roger L. (committee member), Vandsburger, Uri (committee member), Ekkad, Srinath V. (committee member), Paul, Mark R. (committee member).
Subjects/Keywords: Large Eddy Simulation; Wall layer modeling; Synthetic eddy method
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Patil, S. (2011). Large Eddy Simulations of high Reynolds number Complex Flows with Synthetic Inlet Turbulence. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26060
Chicago Manual of Style (16th Edition):
Patil, Sunil. “Large Eddy Simulations of high Reynolds number Complex Flows with Synthetic Inlet Turbulence.” 2011. Doctoral Dissertation, Virginia Tech. Accessed February 27, 2021.
http://hdl.handle.net/10919/26060.
MLA Handbook (7th Edition):
Patil, Sunil. “Large Eddy Simulations of high Reynolds number Complex Flows with Synthetic Inlet Turbulence.” 2011. Web. 27 Feb 2021.
Vancouver:
Patil S. Large Eddy Simulations of high Reynolds number Complex Flows with Synthetic Inlet Turbulence. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/10919/26060.
Council of Science Editors:
Patil S. Large Eddy Simulations of high Reynolds number Complex Flows with Synthetic Inlet Turbulence. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/26060
University of Minnesota
11.
Komives, Jeffrey.
Development and Validation of a Turbulence Wall Model for Compressible Flows with Heat Transfer.
Degree: PhD, Aerospace Engineering and Mechanics, 2016, University of Minnesota
URL: http://hdl.handle.net/11299/182810
► The computational cost to model high Reynolds number flows of engineering interest scales poorly with problem size and is excessively expensive. This fact motivates the…
(more)
▼ The computational cost to model high Reynolds number flows of engineering interest scales poorly with problem size and is excessively expensive. This fact motivates the development of turbulence wall models to lessen the computational burden. These models aim to provide accurate wall flux quantification on computational meshes that would otherwise be unable to accurately estimate these quantities. The benefit of using such an approximation is that the height of the wall-adjacent computational elements can be increased by one to two orders of magnitude, allowing for comparable increases in stable explicit timestep. This increase in timestep is critically necessary for the large eddy simulation of high Reynolds number turbulent flows. To date, most research in the application of wall models has focused on incompressible flows or flows with very weak compressibility. Very few studies examine the applicability of wall models to flows with significant compressibility and heat transfer. The present work details the derivation of a wall model appropriate for compressible flows with heat transfer. The model framework allows for the inclusion of non-equilibrium terms in the determination of wall shear and heat transfer. The model is applied to a variety of supersonic and hypersonic flows, and is studied in both Reynolds-averaged simulations and large eddy simulations. The impact of several modeling approaches and model terms is examined. The wall-modeled calculations show excellent agreement with wall-resolved calculations and experimental data. For time accurate calculations, the use of the wall model allows for explicit timesteps more than 20 times larger than that of the wall-resolved calculation, significantly reducing both the cost of the calculation and the time required converge the solution.
Subjects/Keywords: Computational Fluid Dynamics; Fluid Dynamics; Large Eddy Simulation; Simulation; Turbulence
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Komives, J. (2016). Development and Validation of a Turbulence Wall Model for Compressible Flows with Heat Transfer. (Doctoral Dissertation). University of Minnesota. Retrieved from http://hdl.handle.net/11299/182810
Chicago Manual of Style (16th Edition):
Komives, Jeffrey. “Development and Validation of a Turbulence Wall Model for Compressible Flows with Heat Transfer.” 2016. Doctoral Dissertation, University of Minnesota. Accessed February 27, 2021.
http://hdl.handle.net/11299/182810.
MLA Handbook (7th Edition):
Komives, Jeffrey. “Development and Validation of a Turbulence Wall Model for Compressible Flows with Heat Transfer.” 2016. Web. 27 Feb 2021.
Vancouver:
Komives J. Development and Validation of a Turbulence Wall Model for Compressible Flows with Heat Transfer. [Internet] [Doctoral dissertation]. University of Minnesota; 2016. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/11299/182810.
Council of Science Editors:
Komives J. Development and Validation of a Turbulence Wall Model for Compressible Flows with Heat Transfer. [Doctoral Dissertation]. University of Minnesota; 2016. Available from: http://hdl.handle.net/11299/182810
12.
Fernandes, Royston.
Wind erosion in presence of vegetation : Erosion éolienne en présence de végétation.
Degree: Docteur es, Physique de l'environnement, 2019, Bordeaux
URL: http://www.theses.fr/2019BORD0194
► La poussière minérale atmosphérique résultant de l’érosion éolienne des sols affecte le système terrestre. La distribution en taille (PSD) de cette poussière joue un rôle…
(more)
▼ La poussière minérale atmosphérique résultant de l’érosion éolienne des sols affecte le système terrestre. La distribution en taille (PSD) de cette poussière joue un rôle clé dans le bilan radiatif et la chimie atmosphérique, la formation des nuages et la productivité des écosystèmes terrestres et marins. Néanmoins les modèles climatiques peinent à reproduire précisément la PSD de la poussière émise. Ceci vient de la représentation imparfaite des mécanismes d’émission de poussières et des vitesses de vent de surface associées. C’est particulièrement vrai en présence d’éléments de rugosité de surface comme la végétation en régions semi-arides. Cette thèse vise à améliorer la compréhension de l’émission de poussière en environnements semi-arides, caractérisé par des surfaces hétérogènes liées à la végétation saisonnière éparse. A cette fin, une combinaison d’expériences numériques et de terrain a été employée, en partant d’un sol nu érodable à des surfaces couvertes de végétation éparse.Une revue des schémas existants a montré des ambiguïtés dans la paramétrisation des processus influençant l’émission de poussières. Une analyse de sensibilité utilisant un modèle 1D de dispersion de poussière a démontré l’importance (i) de la PSD de la poussière à la surface et de la paramétrisation de la cohésion interparticules qui affectent la PSD de la poussière émise, et (ii) des processus de dépôt qui influencent la PSD du flux net de poussière dans la couche de surface atmosphérique. A partir de cette analyse, un nouveau schéma d’émission a été incorporé à un modèle 3D d’érosion, couplé à un modèle turbulent
Large Eddy Simulation (LES), et évalué d’abord sur une surface nue sur la base de l’expérimentation WIND-O-V 2017 en Tunisie. Le modèle a ainsi été capable de reproduire la dissimilarité entre les transports turbulents de poussière et de quantité de mouvement dans la couche de surface, observée durant l’expérience. Cela signifie que poussière et quantité de mouvement ne sont pas toujours transportées par les mêmes tourbillons. Le modèle a démontré que la cause principale de cette dissimilarité est l’intermittence de l’émission de poussières, qui varie avec l’intensité du vent et le fetch.L’impact de la végétation éparse sur le flux net de poussière émis a ensuite été étudié sur la base de l’expérimentation WIND-O-V 2018, conduite sur le même site que celle de 2017. Les mesures ont été utilisées pour évaluer le modèle 3D d’érosion incluant les caractéristiques de la végétation. La comparaison entre les expérimentations 2017 et 2018 a confirmé que la végétation éparse réduit l’émission en augmentant la vitesse de frottement seuil de l’érosion, qui dépend des caractéristiques de la végétation et de la direction du vent. Au cours de l’expérimentation 2018, nous avons observé que la PSD du flux net de poussière émis variait, contrairement à 2017, avec un appauvrissement progressif en grosses particules (1.50 µm). Il s’est avéré que cet appauvrissement n’était pas lié à la présence de végétation, mais à l'épuisement du sol en…
Advisors/Committee Members: Dupont, Sylvain (thesis director), Lamaud, Eric (thesis director).
Subjects/Keywords: Erosion éolienne; Large-Eddy Simulation; Turbulence; Saltation; Flux de poussière; Végétation; Wind erosion; Large-Eddy Simulation; Turbulence; Saltation; Dust Flux; Vegetation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Fernandes, R. (2019). Wind erosion in presence of vegetation : Erosion éolienne en présence de végétation. (Doctoral Dissertation). Bordeaux. Retrieved from http://www.theses.fr/2019BORD0194
Chicago Manual of Style (16th Edition):
Fernandes, Royston. “Wind erosion in presence of vegetation : Erosion éolienne en présence de végétation.” 2019. Doctoral Dissertation, Bordeaux. Accessed February 27, 2021.
http://www.theses.fr/2019BORD0194.
MLA Handbook (7th Edition):
Fernandes, Royston. “Wind erosion in presence of vegetation : Erosion éolienne en présence de végétation.” 2019. Web. 27 Feb 2021.
Vancouver:
Fernandes R. Wind erosion in presence of vegetation : Erosion éolienne en présence de végétation. [Internet] [Doctoral dissertation]. Bordeaux; 2019. [cited 2021 Feb 27].
Available from: http://www.theses.fr/2019BORD0194.
Council of Science Editors:
Fernandes R. Wind erosion in presence of vegetation : Erosion éolienne en présence de végétation. [Doctoral Dissertation]. Bordeaux; 2019. Available from: http://www.theses.fr/2019BORD0194
University of Colorado
13.
Coley, Christopher Joel.
Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/220
► In this dissertation, a class of methods which combines divergence-conforming discretizations with residual-based subgrid modeling for large eddy simulation of turbulent flows is introduced.…
(more)
▼ In this dissertation, a class of methods which combines divergence-conforming discretizations with residual-based subgrid modeling for
large eddy simulation of turbulent flows is introduced. These methods fall within two frameworks: residual-based variational multiscale methods and residual-based
eddy viscosities. These methods utilize variationally-consistent formulations for the fine-scale velocities in order to construct subgrid-scale models based on the coarse-scale residual. The result is an LES methodology that responds naturally to spatially- and temporally-varying turbulence. Numerical results demonstrate that these new methods demonstrate proper behavior for homogeneous turbulence and outperform classical LES models for transitional flows and wall-bounded turbulent flows. Furthermore, the resulting formulations contain no "tunable'' parameters, and thus extend generally across various classes of flow. Additionally, a differential variational multiscale method in which the unresolved fine-scales are approximated element-wise using a discontinuous Galerkin method is presented and examined. Stability and convergence results for the methodology as applied to the scalar transport problem are established, and it is proven that the method exhibits optimal convergence rates in the SUPG norm and is robust with respect to the Péclet number if the discontinuous subscale approximation space is sufficiently rich. The method is applied to isogeometric NURBS discretizations of steady and unsteady transport problems, and the corresponding numerical results demonstrate that the method is stable and accurate in the advective limit even when low-order discontinuous subscale approximations are employed. Based on these promising results, a class of differential subgrid vortex models for
large eddy simulation of turbulent flows is proposed. Finally, the underlying discretization utilized by the simulations here offers the opportunity to develop efficient new geometric multigrid linear solvers. In this regard, a geometric multigrid methodology for the solution of matrix systems associated with isogeometric compatible discretizations of the generalized Stokes and Oseen problems is presented. The methodology provably yields a pointwise divergence-free velocity field independent of the number of pre-smoothing steps, post-smoothing steps, grid levels, or cycles in a V-cycle implementation. The methodology relies upon Scwharz-style smoothers in conjunction with specially defined overlapping subdomains that respect the underlying topological structure of the generalized Stokes and Oseen problems. Numerical results in both two- and three-dimensions demonstrate the robustness of the methodology through the invariance of convergence rates with respect to grid resolution and flow parameters for the generalized Stokes problem as well as the generalized Oseen problem, provided it is not advection-dominated.
Advisors/Committee Members: John A. Evans, Kenneth Jansen, Carlos Felippa, Peter Hamlington, Yuri Bazilevs.
Subjects/Keywords: divergence-conforming; large eddy simulation; residual-based large eddy simulation; structure-preserving; turbulence modeling; variational multiscale method; Aerospace Engineering; Applied Mathematics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Coley, C. J. (2017). Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/220
Chicago Manual of Style (16th Edition):
Coley, Christopher Joel. “Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations.” 2017. Doctoral Dissertation, University of Colorado. Accessed February 27, 2021.
https://scholar.colorado.edu/asen_gradetds/220.
MLA Handbook (7th Edition):
Coley, Christopher Joel. “Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations.” 2017. Web. 27 Feb 2021.
Vancouver:
Coley CJ. Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Feb 27].
Available from: https://scholar.colorado.edu/asen_gradetds/220.
Council of Science Editors:
Coley CJ. Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/asen_gradetds/220
University of Colorado
14.
Coley, Christopher Joel.
Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/172
► In this dissertation, a class of methods which combines divergence-conforming discretizations with residual-based subgrid modeling for large eddy simulation of turbulent flows is introduced.…
(more)
▼ In this dissertation, a class of methods which combines divergence-conforming discretizations with residual-based subgrid modeling for
large eddy simulation of turbulent flows is introduced. These methods fall within two frameworks: residual-based variational multiscale methods and residual-based
eddy viscosities. These methods utilize variationally-consistent formulations for the fine-scale velocities in order to construct subgrid-scale models based on the coarse-scale residual. The result is an LES methodology that responds naturally to spatially- and temporally-varying turbulence. Numerical results demonstrate that these new methods demonstrate proper behavior for homogeneous turbulence and outperform classical LES models for transitional flows and wall-bounded turbulent flows. Furthermore, the resulting formulations contain no ``tunable'' parameters, and thus extend generally across various classes of flow. [object Object] Additionally, a differential variational multiscale method in which the unresolved fine-scales are approximated element-wise using a discontinuous Galerkin method is presented and examined. Stability and convergence results for the methodology as applied to the scalar transport problem are established, and it is proven that the method exhibits optimal convergence rates in the SUPG norm and is robust with respect to the Péclet number if the discontinuous subscale approximation space is sufficiently rich. The method is applied to isogeometric NURBS discretizations of steady and unsteady transport problems, and the corresponding numerical results demonstrate that the method is stable and accurate in the advective limit even when low-order discontinuous subscale approximations are employed. Based on these promising results, a class of differential subgrid vortex models for
large eddy simulation of turbulent flows is proposed. Finally, the underlying discretization utilized by the simulations here offers the opportunity to develop efficient new geometric multigrid linear solvers. In this regard, a geometric multigrid methodology for the solution of matrix systems associated with isogeometric compatible discretizations of the generalized Stokes and Oseen problems is presented. The methodology provably yields a pointwise divergence-free velocity field independent of the number of pre-smoothing steps, post-smoothing steps, grid levels, or cycles in a V-cycle implementation. The methodology relies upon Scwharz-style smoothers in conjunction with specially defined overlapping subdomains that respect the underlying topological structure of the generalized Stokes and Oseen problems. Numerical results in both two- and three-dimensions demonstrate the robustness of the methodology through the invariance of convergence rates with respect to grid resolution and flow parameters for the generalized Stokes problem as well as the generalized Oseen problem, provided it is not advection-dominated.
Advisors/Committee Members: John A. Evans, Kenneth Jansen, Carlos Felippa, Peter Hamlington, Yuri Bazilevs.
Subjects/Keywords: Divergence-conforming; Large eddy simulation; Residual-based large eddy simulation; Structure-preserving; Turbulence modeling; Variational multiscale method; Aerospace Engineering
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Coley, C. J. (2017). Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/172
Chicago Manual of Style (16th Edition):
Coley, Christopher Joel. “Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations.” 2017. Doctoral Dissertation, University of Colorado. Accessed February 27, 2021.
https://scholar.colorado.edu/asen_gradetds/172.
MLA Handbook (7th Edition):
Coley, Christopher Joel. “Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations.” 2017. Web. 27 Feb 2021.
Vancouver:
Coley CJ. Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Feb 27].
Available from: https://scholar.colorado.edu/asen_gradetds/172.
Council of Science Editors:
Coley CJ. Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/asen_gradetds/172
Brno University of Technology
15.
Volavý, Jaroslav.
Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation: Large Eddy Simulation of Turbulent Two-Phase Flow.
Degree: 2019, Brno University of Technology
URL: http://hdl.handle.net/11012/28003
► Doctoral thesis deals with the numerical simulations of two-phase flows, especially with prediction of movement of dispersed phase (particles) carried by fluid. The Euler-Lagrange approach…
(more)
▼ Doctoral thesis deals with the numerical simulations of two-phase flows, especially with prediction of movement of dispersed phase (particles) carried by fluid. The Euler-Lagrange approach was applied for description of the system fluid-particles. It means that the fluid is considered to be continuum and its movement is described using Euler approach. Particles are regarded as mass points and their movement is solved using Lagrangian approach. The
Large Eddy Simulation method was adopted for solution of the fluid flow. The series of simulations of the backward-facing step flow laden with particles were performed. The concentration of the particles in the flow was high enough for consideration of the influence of particles on the turbulence of the carrier phase. The developed scheme for generation of turbulence on the inlet is applied. The influence of anisotropic decomposition of subgrid energy on movement of particles was studied in the frame of this work.
Advisors/Committee Members: Jícha, Miroslav (advisor), Fürst, Jiří (referee), Vimmr, Jan (referee).
Subjects/Keywords: Large Eddy Simulation; turbulence na vstupu; dvoufázové proudění; modulace turbulence; Large Eddy Simulation; inlet boundary condition; two-phase flow; turbulence modulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Volavý, J. (2019). Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation: Large Eddy Simulation of Turbulent Two-Phase Flow. (Thesis). Brno University of Technology. Retrieved from http://hdl.handle.net/11012/28003
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Volavý, Jaroslav. “Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation: Large Eddy Simulation of Turbulent Two-Phase Flow.” 2019. Thesis, Brno University of Technology. Accessed February 27, 2021.
http://hdl.handle.net/11012/28003.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Volavý, Jaroslav. “Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation: Large Eddy Simulation of Turbulent Two-Phase Flow.” 2019. Web. 27 Feb 2021.
Vancouver:
Volavý J. Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation: Large Eddy Simulation of Turbulent Two-Phase Flow. [Internet] [Thesis]. Brno University of Technology; 2019. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/11012/28003.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Volavý J. Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation: Large Eddy Simulation of Turbulent Two-Phase Flow. [Thesis]. Brno University of Technology; 2019. Available from: http://hdl.handle.net/11012/28003
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Virginia Tech
16.
Dilip, Deepu.
Wall Modeled Large Eddy Simulation of Flow over a Wall Mounted Hump.
Degree: MS, Mechanical Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/64356
► Large Eddy Simulation (LES) is a relatively more accurate and reliable alternative to solution of Reynolds Averaged Navier Stokes (RANS) equations in simulating complex turbulent…
(more)
▼ Large Eddy Simulation (LES) is a relatively more accurate and reliable alternative to solution of Reynolds Averaged Navier Stokes (RANS) equations in simulating complex turbulent flows at a lesser computational cost than a direct numerical
simulation (DNS). However, LES of wall-bounded flows still requires a very high grid resolution in the inner wall layer making its widespread use difficult. Different attempts have been made in the past time to overcome this problem by modeling the near wall turbulence instead of resolving it. One such approach is a two-layer wall model that solves for a reduced one-dimensional equation in the inner wall layer, while solving for the filtered Navier-Stokes equations in the outer layer. The use of such a model allows for a coarser grid resolution than a wall resolved LES.
This work validates the performance of a two-layer wall model developed for an arbitrary body fitted non-orthogonal grid in the flow over a wall mounted hump at Reynolds number 9.36x105. The wall modeled
large eddy simulation (WMLES) relaxes the grid requirement compared to a wall resolved LES (WRLES) by allowing the first off-wall grid point to be placed at a y+ of approximately 20-40. It is found that the WMLES results are general good agreement with WRLES and experiments. Surface pressure coefficient, skin friction, mean velocity profiles, and the reattachment location compare very well with experiment. The WMLES and WRLES exhibit some under prediction of the peak values in the turbulent quantities close to the reattachment location, with better agreement with the experiment in the separated region. In contrast, a
simulation that did not employ the wall model on the grid used for WMLES failed to predict flow separation and showed
large discrepancies with the experimental data. In addition to the relaxation of the grid requirement in the wall normal direction, it was also observed that the wall model allowed a reduction in the number of computational cells in the span-wise direction by half. However an LES calculation on a grid with reduced number of cells in span-wise direction turned unstable almost immediately, thereby highlighting the effectiveness of the wall model. Besides reducing the number of grid points in the spatial domain, the relaxed grid resolution for the WMLES also permitted the use of a larger time step. This resulted in an order of magnitude reduction in the total CPU time relative to WRLES.
Advisors/Committee Members: Tafti, Danesh K. (committeechair), Dancey, Clinton L. (committee member), Paul, Mark R. (committee member).
Subjects/Keywords: Computational Fluid Dynamics; Wall resolved Large Eddy Simulation; Wall Modeled Large Eddy Simulation; Two-layer Wall Model; Wall mounted hump
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Dilip, D. (2014). Wall Modeled Large Eddy Simulation of Flow over a Wall Mounted Hump. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/64356
Chicago Manual of Style (16th Edition):
Dilip, Deepu. “Wall Modeled Large Eddy Simulation of Flow over a Wall Mounted Hump.” 2014. Masters Thesis, Virginia Tech. Accessed February 27, 2021.
http://hdl.handle.net/10919/64356.
MLA Handbook (7th Edition):
Dilip, Deepu. “Wall Modeled Large Eddy Simulation of Flow over a Wall Mounted Hump.” 2014. Web. 27 Feb 2021.
Vancouver:
Dilip D. Wall Modeled Large Eddy Simulation of Flow over a Wall Mounted Hump. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/10919/64356.
Council of Science Editors:
Dilip D. Wall Modeled Large Eddy Simulation of Flow over a Wall Mounted Hump. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/64356
Loughborough University
17.
Coates, Tim.
Numerical simulation of unconventional aero-engine exhaust systems for aircraft.
Degree: PhD, 2014, Loughborough University
URL: http://hdl.handle.net/2134/16365
► This thesis investigates the impact of upstream duct convolution on the plume development for high speed jets. In particular, investigations are carried out into an…
(more)
▼ This thesis investigates the impact of upstream duct convolution on the plume development for high speed jets. In particular, investigations are carried out into an unconventional aero-engine exhaust systems comprised of a modified convergent-divergent rectangular nozzle where the converging section of the nozzle includes an S-bend in the duct. The motivation for this work comes from both the military and civilian sectors of the aerospace industry. The growing interest into highly efficient engines in the civilian sector and increasing complexities involved in stealth technologies for military applications has led to new design constraints on aero-engine exhaust systems that require further research into flows through more complex duct geometries. Due to a lack of experimental data into this area in the open literature validation studies are undertaken into flows through an S-bend duct and exhaust plume development from a rectangular convergent-divergent nozzle. The validation work is simulated using RANS CFD with common industrial turbulence models as well as LES with artificial inlet conditions. Subsequently, a CFD investigation into three unconventional aero-engine exhaust systems, with over-expanded conditions, with differing angles of curvature across the converging S-bend is undertaken using both RANS and LES methodologies governed by the validation work. As the curvature of the S-bend was increased it was found that the thrust and effective NPR both decrease. Whilst these changes were within acceptable levels (with some optimisation) for a circumferential extent of up to 53.1 the losses became prohibitive large at extents. For the ducts with a greater circumferential extents separation was seen to occur at the throat of the nozzle; this changes the design parameters of the nozzle leading to a higher Mach number and could potentially be harnessed to improve performance of the engine creating a `variable throat' nozzle. The impact of using different numerical solvers to simulate the flow through an unconventional aero-engine exhaust system has also been considered. The use of LES has shown that the octagonal, hexahedral and trapezoidal shapes initially observed in the development of the plumes of the RANS cases are likely to be an artifact caused by the RANS solver, as would the transverse total pressure gradients observed in the RANS cases at the nozzle exit as they are both absent from all of the LES results. Likewise the implementation of realistic inlet conditions has a significant impact on the development of the plume, particularly in the length of the potential core and the number of shock cells.
Subjects/Keywords: 629.13; Large eddy simulation; S-bend; Supersonic; Propulsion; Gas turbine; Synthetic eddy method
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Coates, T. (2014). Numerical simulation of unconventional aero-engine exhaust systems for aircraft. (Doctoral Dissertation). Loughborough University. Retrieved from http://hdl.handle.net/2134/16365
Chicago Manual of Style (16th Edition):
Coates, Tim. “Numerical simulation of unconventional aero-engine exhaust systems for aircraft.” 2014. Doctoral Dissertation, Loughborough University. Accessed February 27, 2021.
http://hdl.handle.net/2134/16365.
MLA Handbook (7th Edition):
Coates, Tim. “Numerical simulation of unconventional aero-engine exhaust systems for aircraft.” 2014. Web. 27 Feb 2021.
Vancouver:
Coates T. Numerical simulation of unconventional aero-engine exhaust systems for aircraft. [Internet] [Doctoral dissertation]. Loughborough University; 2014. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/2134/16365.
Council of Science Editors:
Coates T. Numerical simulation of unconventional aero-engine exhaust systems for aircraft. [Doctoral Dissertation]. Loughborough University; 2014. Available from: http://hdl.handle.net/2134/16365
18.
Graham, Jason Scott.
Turbulence simulations: multiscale modeling and data-intensive computing methodologies.
Degree: 2014, Johns Hopkins University
URL: http://jhir.library.jhu.edu/handle/1774.2/37045
► In this two part work, methodologies for the multiscale modeling of complex turbulent flows and data-intensive computing strategies for large-scale turbulent simulations are developed and…
(more)
▼ In this two part work, methodologies for the multiscale modeling of complex turbulent flows and data-intensive computing strategies for
large-scale turbulent simulations are developed and presented. The first part of this thesis is devoted to the
simulation of turbulent flows over objects characterized by hierarchies of length-scale. Flows of this type present special challenges associated with the cost of resolving small-scale geometric elements. During
large eddy simulation (LES), their effects on the resolved scales must be captured realistically through subgrid-scale models. Prior work performed by Chester et al., J. Comput. Phys. 2007 proposed a technique called renormalized numerical
simulation (RNS), which is applicable to objects that display scale-invariant geometric (fractal) properties. The idea of RNS is similar to that of the dynamic model used in LES to determine model parameters for the subgrid-stress tensor model in the bulk of the flow. In RNS, drag
forces from the resolved elements that are obtained during the
simulation are re-scaled appropriately by determining drag coefficients that are then applied to specify the drag forces associated with the subgrid-scale elements. In the current work we introduce a generalized framework for describing and implementing the RNS methodology thereby extending the methodology first presented by Chester et al., 2007. Furthermore, we present various other possible practical implementations of RNS that differ on important, technical aspects related to 1) time averaging, 2) spatial localization, and 3) numerical representation of the drag forces. The new RNS framework is then applied to fractal tree canopies consisting of fractal-like trees with both planar cross-section and three dimensional orientations. The results indicate that the propsed time averaged, local, and explicit formulation of RNS is superior to the predecessor formulation as it enables the modeling of spatially non-homogenous
geometries without using a low-level branch based description and preserves the assumed dynamic similary through temporal filtering. In addition, the overall predicted drag force of the non-planar fractal trees is shown to agree well with experimental data. In addition to RNS, a methodology for generating accurate inflow conditions in multiscale turbulence simulations is present. This technique called concurrent precursor
simulation (CPS) allows the synchronous generation of inflow data from an upstream precursor
simulation. This approach conceptually is the same as the standard precursor simulations (Lund et al., J. Comput. Phys. 1998 and Ferrante et al., J. Comput. Phys. 2004) used in the past, however, it eliminates the I/O bottleneck of disk reads and writes by transferring sampled data directly between domains using MPI. Furthermore, issues with recycling time scales of the sample inflow library are removed since the upstream, precursor
simulation is performed concurrently with
the target
simulation. This methodology is applied to a single fractal tree (modeled using RNS)…
Advisors/Committee Members: Meneveau, Charles (advisor).
Subjects/Keywords: turbulence;
numerical simulation;
large eddy simulation;
direct numerical simulation;
subgrid-scale modeling;
data-intensive computing
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Graham, J. S. (2014). Turbulence simulations: multiscale modeling and data-intensive computing methodologies. (Thesis). Johns Hopkins University. Retrieved from http://jhir.library.jhu.edu/handle/1774.2/37045
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Graham, Jason Scott. “Turbulence simulations: multiscale modeling and data-intensive computing methodologies.” 2014. Thesis, Johns Hopkins University. Accessed February 27, 2021.
http://jhir.library.jhu.edu/handle/1774.2/37045.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Graham, Jason Scott. “Turbulence simulations: multiscale modeling and data-intensive computing methodologies.” 2014. Web. 27 Feb 2021.
Vancouver:
Graham JS. Turbulence simulations: multiscale modeling and data-intensive computing methodologies. [Internet] [Thesis]. Johns Hopkins University; 2014. [cited 2021 Feb 27].
Available from: http://jhir.library.jhu.edu/handle/1774.2/37045.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Graham JS. Turbulence simulations: multiscale modeling and data-intensive computing methodologies. [Thesis]. Johns Hopkins University; 2014. Available from: http://jhir.library.jhu.edu/handle/1774.2/37045
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Utah
19.
Shingleton, Nick.
Coupling a land-surface model to large-eddy simulation to study the nocturnal boundary layer.
Degree: MS;, Mechanical Engineering;, 2010, University of Utah
URL: http://content.lib.utah.edu/cdm/singleitem/collection/etd2/id/2132/rec/266
► Negatively buoyant forces in the stable boundary layer (SBL) damp turbulent motions, resulting in decreased transport of momentum, heat and water vapor. During high levels…
(more)
▼ Negatively buoyant forces in the stable boundary layer (SBL) damp turbulent motions, resulting in decreased transport of momentum, heat and water vapor. During high levels of stratification this can cause intermittent turbulence, gravity waves and weak turbulent fluxes. In some cases, decoupling between the atmospheric boundary layer (ABL) and land-atmosphere fluxes can occur. Accurately reproducing these phenomena requires detailed treatment of the physical processes that govern the two-way dynamic interaction between surface properties and the ABL. Increasingly, large-eddy simulation (LES) is used to study land-atmosphere interactions in the SBL. In these studies, the dominant treatment of surface boundary conditions is to specify a known state or flux. This research uses LES that is fully coupled to a land-surface model (LSM) to investigate the SBL. The LSM explicitly solves for the transport of heat and water in a one-dimensional column of the upper soil. Coupling to the atmosphere is achieved through a surface budget, which partitions the available radiative forcing into ground heat flux and sensible and latent heat fluxes. Turbulent boundary layer profiles and surface fluxes are compared to field data and results from simulations of the GABLS3 LES intercomparison case.
Subjects/Keywords: Land-surface model; Large-eddy simulation; Nocturnal; Stable
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Shingleton, N. (2010). Coupling a land-surface model to large-eddy simulation to study the nocturnal boundary layer. (Masters Thesis). University of Utah. Retrieved from http://content.lib.utah.edu/cdm/singleitem/collection/etd2/id/2132/rec/266
Chicago Manual of Style (16th Edition):
Shingleton, Nick. “Coupling a land-surface model to large-eddy simulation to study the nocturnal boundary layer.” 2010. Masters Thesis, University of Utah. Accessed February 27, 2021.
http://content.lib.utah.edu/cdm/singleitem/collection/etd2/id/2132/rec/266.
MLA Handbook (7th Edition):
Shingleton, Nick. “Coupling a land-surface model to large-eddy simulation to study the nocturnal boundary layer.” 2010. Web. 27 Feb 2021.
Vancouver:
Shingleton N. Coupling a land-surface model to large-eddy simulation to study the nocturnal boundary layer. [Internet] [Masters thesis]. University of Utah; 2010. [cited 2021 Feb 27].
Available from: http://content.lib.utah.edu/cdm/singleitem/collection/etd2/id/2132/rec/266.
Council of Science Editors:
Shingleton N. Coupling a land-surface model to large-eddy simulation to study the nocturnal boundary layer. [Masters Thesis]. University of Utah; 2010. Available from: http://content.lib.utah.edu/cdm/singleitem/collection/etd2/id/2132/rec/266
20.
Majander, Petri.
Large-Eddy Simulation of a Round Jet in a Cross-Flow.
Degree: 2006, Helsinki University of Technology
URL: http://lib.tkk.fi/Diss/2006/isbn9512284057/
► Several aspects of large-eddy simulations (LES) are studied in this thesis. In the first part computational requirements and methods are compared for the calculation of…
(more)
▼ Several aspects of large-eddy simulations (LES) are studied in this thesis. In the first part computational requirements and methods are compared for the calculation of unsteady incompressible flow. Explicit time integration methods are efficient especially in simple flow geometries and with low Reynolds numbers. An Adams-Bashford fractional time-stepping scheme is used in the turbulent channel flow computations. The Smagorinsky model is a baseline subgrid-scale model used in LES. This and the dynamic version are assessed in a turbulent channel flow. The models do not necessarily improve the results at a low Reynolds number if the calculation is stabilized enough by the molecular or numerical viscous effects. With the second-order central scheme the numerical error is estimated to be greater than the filtered stresses from the momentum equations. This estimate alone suggests that there is no accurate model for instantaneous stresses for the low-order schemes. The main role of the subgrid-scale model is to remove energy from the resolved scales and hence to stabilize the calculation. LES in any practical application, even at a low-Reynolds number, requires high computational resources. A parallel solver based on a multi-block approach is written, where computational domain is divided between many structured blocks. The blocks assigned to different processors communicate at the boundaries with an MPI standard. The solver is tested with a turbulent cavity and a pipe flow. A linear speed-up and scale-up are achieved with equally balanced processors loads. A large-eddy simulation of a round jet penetrating normally into a cross-flow is computed. The jet-to-cross-flow velocity ratio is 2.3 at a Reynolds number of 46 700, based on the jet bulk velocity and the jet diameter. The simulation is performed both with a steady and an unsteady boundary condition at the jet inlet pipe. A passive scalar is discretized both with a central and a TVD discretization. The results are compared with each other and the experimental measurements of Crabb, Durão and Whitelaw. The computation reproduced many phenomena present in such a flow, like the shear layer ring vortices and a counter-rotating vortex pair. In general, a reasonable agreement with the measurements was obtained. The unsteady boundary condition at the jet inlet increases the spreading of the jet slightly.
Tässä väitöstyössä tutkitaan ja sovelletaan suurten pyörteiden menetelmää (large-eddy simulation, LES). Ensimmäisessä osassa tutkitaan aikaintegrointimenetelmiä. Alhaisella Reynoldsin luvulla ja yksinkertaisella virtausgeometrialla eksplisiittiset menetelmät ovat huomattavasti nopeampia kuin vaihtoehtona kokeiltu implisiittinen menetelmä. Adams-Bashford-menetelmää käytetään turbulentin kanavavirtauksen laskentaan. Smagorinski-malli on yleisimmin käytetty alihilamalli LES:ssa. Tätä ja sen dynaamista versiota kokeillaan turbulentissa kanavavirtauksessa. Alihilamalli ei välttämättä paranna simulointitulosta alhaisella Reynoldsin luvulla, jos molekyläärinen tai numeerinen…
Advisors/Committee Members: Helsinki University of Technology, Department of Mechanical Engineering, Laboratory of Applied Thermodynamics.
Subjects/Keywords: large-eddy simulation; jet in a cross-flow
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Majander, P. (2006). Large-Eddy Simulation of a Round Jet in a Cross-Flow. (Thesis). Helsinki University of Technology. Retrieved from http://lib.tkk.fi/Diss/2006/isbn9512284057/
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Majander, Petri. “Large-Eddy Simulation of a Round Jet in a Cross-Flow.” 2006. Thesis, Helsinki University of Technology. Accessed February 27, 2021.
http://lib.tkk.fi/Diss/2006/isbn9512284057/.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Majander, Petri. “Large-Eddy Simulation of a Round Jet in a Cross-Flow.” 2006. Web. 27 Feb 2021.
Vancouver:
Majander P. Large-Eddy Simulation of a Round Jet in a Cross-Flow. [Internet] [Thesis]. Helsinki University of Technology; 2006. [cited 2021 Feb 27].
Available from: http://lib.tkk.fi/Diss/2006/isbn9512284057/.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Majander P. Large-Eddy Simulation of a Round Jet in a Cross-Flow. [Thesis]. Helsinki University of Technology; 2006. Available from: http://lib.tkk.fi/Diss/2006/isbn9512284057/
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
UCLA
21.
Amouyal, Solal.
Numerical simulation of a closed rotor-stator system using Large Eddy Simulation.
Degree: Aerospace Engineering, 2014, UCLA
URL: http://www.escholarship.org/uc/item/975761j8
► A large eddy simulation of an enclosed annular rotor stator cavity is presented. Thegeometry is characterized by a large aspect ratio G = (b-a)/h =…
(more)
▼ A large eddy simulation of an enclosed annular rotor stator cavity is presented. Thegeometry is characterized by a large aspect ratio G = (b-a)/h = 18.32 and a small radiusratio a/b = 0.152, where a and b are the inner and outer radii of the rotating disk and h isthe interdisk spacing. The rotation rate ω under consideration is equivalent to the rotationalReynolds number Re = ω b<super>2<super> /ν= 9.5x10<super>4<super> , where ν is the kinematic viscosity.The main objective of this study is to correctly simulate the rotor stator cavity using a loworder numerical scheme on unstructured grids. The numerical simulations were run on thesoftware AVBP developed by the Centre Européen de Recherche et de Formation Avancée en Calcul Scientific. The results were compared to the experimental results obtained by Sebastien Poncet of Universit é Aix-Marseille. Two large eddy simulations techniques were used: the Smagorinsky and Wall-adapting local eddy-viscosity models. The simulations were run on three set of grids, each with a different cell resolution-14, 35 and 50- along the thickness of the system. Results from each mesh show a good qualitative agreement of the mean velocity field with Poncet's experimental results. It was found that the Samgorinsky model to be more appropriate for this configuration.
Subjects/Keywords: Aerospace engineering; Large Eddy Simulation; Rotor-stator cavity
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Amouyal, S. (2014). Numerical simulation of a closed rotor-stator system using Large Eddy Simulation. (Thesis). UCLA. Retrieved from http://www.escholarship.org/uc/item/975761j8
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Amouyal, Solal. “Numerical simulation of a closed rotor-stator system using Large Eddy Simulation.” 2014. Thesis, UCLA. Accessed February 27, 2021.
http://www.escholarship.org/uc/item/975761j8.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Amouyal, Solal. “Numerical simulation of a closed rotor-stator system using Large Eddy Simulation.” 2014. Web. 27 Feb 2021.
Vancouver:
Amouyal S. Numerical simulation of a closed rotor-stator system using Large Eddy Simulation. [Internet] [Thesis]. UCLA; 2014. [cited 2021 Feb 27].
Available from: http://www.escholarship.org/uc/item/975761j8.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Amouyal S. Numerical simulation of a closed rotor-stator system using Large Eddy Simulation. [Thesis]. UCLA; 2014. Available from: http://www.escholarship.org/uc/item/975761j8
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Michigan
22.
Tang, Yifeng.
A Nested-LES Approach for Computation of High-Reynolds Number, Equilibrium and Non-Equilibrium Turbulent Wall-Bounded Flows.
Degree: PhD, Mechanical Engineering, 2016, University of Michigan
URL: http://hdl.handle.net/2027.42/120800
► Computation of high Reynolds number, complex, non-equilibrium wall-bounded turbulent flows presents a major challenge for large-eddy simulation (LES), due to the stringent resolution requirements in…
(more)
▼ Computation of high Reynolds number, complex, non-equilibrium wall-bounded turbulent flows presents a major challenge for
large-
eddy simulation (LES), due to the stringent resolution requirements in the near-wall region in conventional LES, and the inability of existing wall models to accurately capture the near-wall dynamics in flows involving complex physics in the near-wall region. In this study, a novel nested-LES approach for computation of high Reynolds number, equilibrium and non-equilibrium, wall-bounded turbulent flows is proposed. The method couples well-resolved LES in a minimal flow unit with coarse-resolution LES in the full domain to provide high-fidelity simulations of the flow physics in both the inner and outer layers. The coupling between the two domains of nested-LES is achieved by dynamically renormalizing the velocity fields in each domain at each time-step during the course of the
simulation to match the wall-normal profiles of the single-time ensemble-averaged kinetic energies of the components of mean and fluctuating velocities in both domains to those of the minimal flow unit in the inner layer, and to those of the full domain in the outer layer. The proposed nested-LES approach can be applied to any flows with at least one direction of local or global homogeneity, while reducing the required number of grid points from O(Re
t2) of conventional LES to O(log{Re
t}) and O(Re
t1) in flows with two or one directions of homogeneity, respectively.
The proposed nested-LES approach has been applied to LES of equilibrium turbulent channel flow at Re
t ~= 1000 - 10000, and non-equilibrium, strained turbulent channel flow at Re
t ~=2000. In application to equilibrium turbulent channel flow, the nested-LES approach predicts the skin-friction coefficient, first-order turbulence statistics, higher-order moments, two-point correlations, correlation maps, and structural features of the flow in agreement with available direct numerical
simulation (DNS) and experimental data. In application to non-equilibrium, strained turbulent channel flow, nested-LES predicts the evolution of skin-friction coefficients and one-point turbulence statistics in good agreement with experimental data in shear-driven, three-dimensional turbulent boundary-layer (TBL).
Advisors/Committee Members: Akhavan, Rayhaneh (committee member), Boyd, John P. (committee member), Dowling, David R. (committee member), Hulbert, Gregory M (committee member).
Subjects/Keywords: turbulence; wall-bounded flow; large-eddy simulation; Mechanical Engineering; Engineering
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Tang, Y. (2016). A Nested-LES Approach for Computation of High-Reynolds Number, Equilibrium and Non-Equilibrium Turbulent Wall-Bounded Flows. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/120800
Chicago Manual of Style (16th Edition):
Tang, Yifeng. “A Nested-LES Approach for Computation of High-Reynolds Number, Equilibrium and Non-Equilibrium Turbulent Wall-Bounded Flows.” 2016. Doctoral Dissertation, University of Michigan. Accessed February 27, 2021.
http://hdl.handle.net/2027.42/120800.
MLA Handbook (7th Edition):
Tang, Yifeng. “A Nested-LES Approach for Computation of High-Reynolds Number, Equilibrium and Non-Equilibrium Turbulent Wall-Bounded Flows.” 2016. Web. 27 Feb 2021.
Vancouver:
Tang Y. A Nested-LES Approach for Computation of High-Reynolds Number, Equilibrium and Non-Equilibrium Turbulent Wall-Bounded Flows. [Internet] [Doctoral dissertation]. University of Michigan; 2016. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/2027.42/120800.
Council of Science Editors:
Tang Y. A Nested-LES Approach for Computation of High-Reynolds Number, Equilibrium and Non-Equilibrium Turbulent Wall-Bounded Flows. [Doctoral Dissertation]. University of Michigan; 2016. Available from: http://hdl.handle.net/2027.42/120800
University of Saskatchewan
23.
Einian, Maryam.
LARGE EDDY SIMULATION OF FLOW AROUND A FINITE SQUARE CYLINDER.
Degree: 2012, University of Saskatchewan
URL: http://hdl.handle.net/10388/ETD-2012-04-443
► The main objective of this research is to develop, document and study numerically the flow around finite-height square cylinders mounted on a ground plane, particularly…
(more)
▼ The main objective of this research is to develop, document and study numerically the flow around finite-height square cylinders mounted on a ground plane, particularly in the near-wake region, under various geometrical conditions. Both the time-averaged and instantaneous flow fields are studied. This thesis consists of three main parts: a comprehensive study of flow over an aspect ratio AR = 5 square cylinder, the effect of sub-grid scale (SGS) models on the numerical
simulation and the effect of aspect ratio on the flow structure.
The first part of the thesis presents the time-averaged and instantaneous flow fields for flow over a wall-mounted finite-height square cylinder of aspect ratio of AR = 5 at a Reynolds number of Re = 500. The time-averaged flow field results are shown to be in good agreement with experiments. Comparison of the time-averaged results with the velocity field for a square cylinder immersed in a thicker boundary layer, suggests that the boundary layer thickness especially affects the upwash flow (Wang et al., 2009). The instantaneous velocity fields provide an in-depth view of the unsteady nature of the flow field. For the flow over a square cylinder of AR = 5, the instantaneous velocity fields are symmetric near the free end. However, antisymmetric patterns observed downstream may be an indication of the presence of periodic von-Karman type vortices.
Since the wake regions are characterized by
large-scale unsteady motions, turbulent flow over bluff bodies is well suited to
large eddy simulation in which the
large energy-containing scales of motion, which are responsible for most of the momentum transport, are resolved whereas the small-scale turbulent fluctuations are modeled. In the second part of the thesis, the performance of the three SGS models, the Smagorinsky model (SM), dynamic Smagorinsky model (DSM) and dynamic non-linear model (DNM) are studied for two grid sets of lower and higher resolution. The results indicated that in case of the DSM insufficient grid resolution leads to erroneous predictions, whereas the DNM is a major improvement as the predictions are similar on both the coarse and fine grids.
In the third and final part of the thesis, the effect of aspect ratio on the flow over a wall-mounted finite-height square cylinder is numerically investigated. The wake of a finite square cylinder is studied for three aspect ratios of AR = 3, 5 and 7. The time-averaged vorticity was shown to vary with aspect ratio, e.g. as the aspect ratio increases, the vortex structures in a horizontal plane at mid-height became shorter and rounder in shape. The flow field of the finite cylinder is known to be strongly affected by the aspect ratio (Adaramola et al., 2006). For cylinders with relatively small aspect ratios, the two ends affect the flow patterns and significantly alter the flow structure.
Advisors/Committee Members: Bergstrom, Donald J., Sumner, David, Bugg, James D., Simonson, Carey J., Spiteri, Raymond J., Yarusevych, Serhiy.
Subjects/Keywords: LARGE EDDY SIMULATION (LES) FINITE SQUARE CYLINDER; BLUFF BODY
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Einian, M. (2012). LARGE EDDY SIMULATION OF FLOW AROUND A FINITE SQUARE CYLINDER. (Thesis). University of Saskatchewan. Retrieved from http://hdl.handle.net/10388/ETD-2012-04-443
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Einian, Maryam. “LARGE EDDY SIMULATION OF FLOW AROUND A FINITE SQUARE CYLINDER.” 2012. Thesis, University of Saskatchewan. Accessed February 27, 2021.
http://hdl.handle.net/10388/ETD-2012-04-443.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Einian, Maryam. “LARGE EDDY SIMULATION OF FLOW AROUND A FINITE SQUARE CYLINDER.” 2012. Web. 27 Feb 2021.
Vancouver:
Einian M. LARGE EDDY SIMULATION OF FLOW AROUND A FINITE SQUARE CYLINDER. [Internet] [Thesis]. University of Saskatchewan; 2012. [cited 2021 Feb 27].
Available from: http://hdl.handle.net/10388/ETD-2012-04-443.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Einian M. LARGE EDDY SIMULATION OF FLOW AROUND A FINITE SQUARE CYLINDER. [Thesis]. University of Saskatchewan; 2012. Available from: http://hdl.handle.net/10388/ETD-2012-04-443
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Tasmania
24.
Conway, AST.
Investigation into wakes generated by surface piercing periscopes.
Degree: 2017, University of Tasmania
URL: https://eprints.utas.edu.au/23968/2/Conway_whole_thesis_ex_pub_mat.pdf
;
https://eprints.utas.edu.au/23968/1/Conway_whole_thesis.pdf
;
Conway,
AST
ORCID:
0000-0002-7346-4725
<https://orcid.org/0000-0002-7346-4725>
2017
,
'Investigation
into
wakes
generated
by
surface
piercing
periscopes',
PhD
thesis,
University
of
Tasmania.
► For operational purposes, submarines are required to pierce the free surface with masts, such as periscopes and snorkels. These masts generate a large plume structure…
(more)
▼ For operational purposes, submarines are required to pierce the free surface with masts, such as periscopes and snorkels. These masts generate a large plume structure which can significantly increase the chance of detection. This thesis develops a numerical technique to accurately model the plume structure generated by a mast piercing the free surface, examining four critical aspects: bow wave height, plume height, plume length, and drag coefficient. The Computational Fluid Dynamics (CFD) model was validated through an experimental programme in a towing tank and against published data. The numerical validation showed that CFD-RANS modelling failed to predict the plume height and plume length while the CFD-LES accurately modelled the plume structure under Froude numbers of 3.0, whilst predicting the overall shape with a small under prediction at Froude numbers greater than 3.0.
The results show aspects of the flow regime within the plume structure and experimental configurations required to accurately replicate real world scenarios. The most critical flow characteristic found for the plume structure was the combination of two flow regimes within the plume structure. The forward section of the plume is generated by the bow wave, whilst the aft section is caused by the submerged section of the mast.
When replicating the mast using a surface piercing cylinder with no end body, it was found that an immersion to depth ratio greater than eight is required to avoid end effects. Additionally, the use of an end body can effectively reduce the impact of the end effect on the plume structure.
Utilising the validated numerical model, several mast configurations were tested in order to reduce the plume signature. Cylindrical double mast configurations and streamlined NACA0012 mast configurations were tested showing potential reductions of the overall plume size. This data can be used to improve the submarine mast configuration, thus reducing the risk of detection due to the generation of a large plume structure.
Subjects/Keywords: Large eddy simulation; free surface; mast; bluff body; plume profile; cylinder
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Conway, A. (2017). Investigation into wakes generated by surface piercing periscopes. (Thesis). University of Tasmania. Retrieved from https://eprints.utas.edu.au/23968/2/Conway_whole_thesis_ex_pub_mat.pdf ; https://eprints.utas.edu.au/23968/1/Conway_whole_thesis.pdf ; Conway, AST ORCID: 0000-0002-7346-4725 <https://orcid.org/0000-0002-7346-4725> 2017 , 'Investigation into wakes generated by surface piercing periscopes', PhD thesis, University of Tasmania.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Conway, AST. “Investigation into wakes generated by surface piercing periscopes.” 2017. Thesis, University of Tasmania. Accessed February 27, 2021.
https://eprints.utas.edu.au/23968/2/Conway_whole_thesis_ex_pub_mat.pdf ; https://eprints.utas.edu.au/23968/1/Conway_whole_thesis.pdf ; Conway, AST ORCID: 0000-0002-7346-4725 <https://orcid.org/0000-0002-7346-4725> 2017 , 'Investigation into wakes generated by surface piercing periscopes', PhD thesis, University of Tasmania..
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Conway, AST. “Investigation into wakes generated by surface piercing periscopes.” 2017. Web. 27 Feb 2021.
Vancouver:
Conway A. Investigation into wakes generated by surface piercing periscopes. [Internet] [Thesis]. University of Tasmania; 2017. [cited 2021 Feb 27].
Available from: https://eprints.utas.edu.au/23968/2/Conway_whole_thesis_ex_pub_mat.pdf ; https://eprints.utas.edu.au/23968/1/Conway_whole_thesis.pdf ; Conway, AST ORCID: 0000-0002-7346-4725 <https://orcid.org/0000-0002-7346-4725> 2017 , 'Investigation into wakes generated by surface piercing periscopes', PhD thesis, University of Tasmania..
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Conway A. Investigation into wakes generated by surface piercing periscopes. [Thesis]. University of Tasmania; 2017. Available from: https://eprints.utas.edu.au/23968/2/Conway_whole_thesis_ex_pub_mat.pdf ; https://eprints.utas.edu.au/23968/1/Conway_whole_thesis.pdf ; Conway, AST ORCID: 0000-0002-7346-4725 <https://orcid.org/0000-0002-7346-4725> 2017 , 'Investigation into wakes generated by surface piercing periscopes', PhD thesis, University of Tasmania.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
25.
Hecht, Nicolas.
Simulation aux grandes échelles des écoulements liquide-gaz : application à l'atomisation : Large eddy simulation for liquid-gas flow : application to atomization.
Degree: Docteur es, Physique. Energétique, 2016, Rouen, INSA
URL: http://www.theses.fr/2016ISAM0026
► Cette thèse est dédiée à l'amélioration des modèles d'atomisation pour les injecteurs automobiles. Le but est de développer et d'évaluer des modèles numériques permettant de…
(more)
▼ Cette thèse est dédiée à l'amélioration des modèles d'atomisation pour les injecteurs automobiles. Le but est de développer et d'évaluer des modèles numériques permettant de capturer le passage de structures liquides en cours d'atomisation depuis les grandes échelles vers les petites échelles de sous-maille dans des configurations complexes. Dans un premier temps, nous mettons en place une procédure de calcul permettant le passage d'une description Eulérienne d'un spray à une procédure Lagrangienne. Afin de ne pas perdre les plus petites structures liquides, celles-ci seront transformées en particules Lagrangienne. Une analyse sur différentes grandeurs physiques, telles que la masse, la quantité de mouvement ou l'énergie cinétique turbulente, lors de cette transformation a été réalisée. L'autre partie de ce travail est consacrée au développement d'un modèle de simulation aux grandes échelles des écoulements diphasiques. La simulation de l'atomisation requiert un traitement spécifique de l'interface. Deux cas limites sont traités dans la littérature : • L'interface peut bien être capturée par le maillage. A ces endroits, une méthode classique de type DNS (Direct Numerical Simulation), comme les méthodes VOF (Volume of Fluid), doit être utilisée. • Lors de la création de plissements inférieurs à la taille de la maille, le maillage ne permet plus de suivre fidèlement l'interface. Il faut alors que le calcul reproduise des résultats d'une méthode LES (Large Eddy Simulation) considérant des structures et des gouttes inférieures à la taille de la maille. Ainsi, la problématique principale consiste à déterminer la configuration dans laquelle se trouve l'interface. La mise en œuvre de ce modèle a permis d'obtenir des résultats dans une configuration proche de l'injection Diesel, qui sont alors comparés à une DNS de référence.
This thesis is dedicated to improve atomization models for automobile injectors. The aim is to develop and evaluate numerical models to capture the liquid structure while they are being atomized from large scales to small sub grid scales in complex configurations. Initially, a calculation procedure is introduced for the transition to an Eulerian description of a spray into a Lagrangian description. In order not to lose the smallest fluid structures, they will be transformed into Lagrangian particles. During this process, an analysis is been performed with various physical parameters such as mass, momentum, or turbulent kinetic energy. The other part of this work is dedicated to the development of a LES (Large Eddy Simulation) for multiphase flow. The simulation of the spray requires a specific treatment of the interface. Two limiting cases are treated in the literature: • The interface may be captured by the mesh. At these locations, a conventional method of DNS (Direct Numerical Simulation) should be used, like the VOF method (Volume of Fluid). • When creating pleating smaller than the size of the mesh, the mesh can no longer match the interface. Then, the calculation must reproduce results from a…
Advisors/Committee Members: Demoulin, François-Xavier (thesis director), Reveillon, Julien (thesis director).
Subjects/Keywords: Méthode de suivi d'interface; LES; Atomization; Large Eddy Simulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hecht, N. (2016). Simulation aux grandes échelles des écoulements liquide-gaz : application à l'atomisation : Large eddy simulation for liquid-gas flow : application to atomization. (Doctoral Dissertation). Rouen, INSA. Retrieved from http://www.theses.fr/2016ISAM0026
Chicago Manual of Style (16th Edition):
Hecht, Nicolas. “Simulation aux grandes échelles des écoulements liquide-gaz : application à l'atomisation : Large eddy simulation for liquid-gas flow : application to atomization.” 2016. Doctoral Dissertation, Rouen, INSA. Accessed February 27, 2021.
http://www.theses.fr/2016ISAM0026.
MLA Handbook (7th Edition):
Hecht, Nicolas. “Simulation aux grandes échelles des écoulements liquide-gaz : application à l'atomisation : Large eddy simulation for liquid-gas flow : application to atomization.” 2016. Web. 27 Feb 2021.
Vancouver:
Hecht N. Simulation aux grandes échelles des écoulements liquide-gaz : application à l'atomisation : Large eddy simulation for liquid-gas flow : application to atomization. [Internet] [Doctoral dissertation]. Rouen, INSA; 2016. [cited 2021 Feb 27].
Available from: http://www.theses.fr/2016ISAM0026.
Council of Science Editors:
Hecht N. Simulation aux grandes échelles des écoulements liquide-gaz : application à l'atomisation : Large eddy simulation for liquid-gas flow : application to atomization. [Doctoral Dissertation]. Rouen, INSA; 2016. Available from: http://www.theses.fr/2016ISAM0026
University of Cambridge
26.
Cocks, Peter.
Large eddy simulation of supersonic combustion with application to scramjet engines.
Degree: PhD, 2011, University of Cambridge
URL: https://doi.org/10.17863/CAM.14003
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541905
► This work evaluates the capabilities of the RANS and LES techniques for the simulation of high speed reacting flows. These methods are used to gain…
(more)
▼ This work evaluates the capabilities of the RANS and LES techniques for the simulation of high speed reacting flows. These methods are used to gain further insight into the physics encountered and regimes present in supersonic combustion. The target application of this research is the scramjet engine, a propulsion system of great promise for efficient hypersonic flight. In order to conduct this work a new highly parallelised code, PULSAR, is developed. PULSAR is capable of simulating complex chemistry combustion in highly compressible flows, based on a second order upwind method to provide a monotonic solution in the presence of high gradient physics. Through the simulation of a non-reacting supersonic coaxial helium jet the RANS method is shown to be sensitive to constants involved in the modelling process. The LES technique is more computationally demanding but is shown to be much less sensitive to these model parameters. Nevertheless, LES results are shown to be sensitive to the nature of turbulence at the inflow; however this information can be experimentally obtained. The SCHOLAR test case is used to validate the reacting aspects of PULSAR. Comparing RANS results from laminar chemistry and assumed PDF combustion model simulations, the influence of turbulence-chemistry interactions in supersonic combustion is shown to be small. In the presence of reactions, the RANS results are sensitive to inflow turbulence, due to its influence on mixing. From complex chemistry simulations the combustion behaviour is evaluated to sit between the flamelet and distributed reaction regimes. LES results allow an evaluation of the physics involved, with a pair of coherent vortices identified as the dominant influence on mixing for the oblique wall fuel injection method. It is shown that inflow turbulence has a significant impact on the behaviour of these vortices and hence it is vital for turbulence intensities and length scales to be measured by experimentalists, in order for accurate simulations to be possible.
Subjects/Keywords: 620; Scramjet; Supersonic combustion; Assumed pdf combustion model; Large eddy simulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Cocks, P. (2011). Large eddy simulation of supersonic combustion with application to scramjet engines. (Doctoral Dissertation). University of Cambridge. Retrieved from https://doi.org/10.17863/CAM.14003 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541905
Chicago Manual of Style (16th Edition):
Cocks, Peter. “Large eddy simulation of supersonic combustion with application to scramjet engines.” 2011. Doctoral Dissertation, University of Cambridge. Accessed February 27, 2021.
https://doi.org/10.17863/CAM.14003 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541905.
MLA Handbook (7th Edition):
Cocks, Peter. “Large eddy simulation of supersonic combustion with application to scramjet engines.” 2011. Web. 27 Feb 2021.
Vancouver:
Cocks P. Large eddy simulation of supersonic combustion with application to scramjet engines. [Internet] [Doctoral dissertation]. University of Cambridge; 2011. [cited 2021 Feb 27].
Available from: https://doi.org/10.17863/CAM.14003 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541905.
Council of Science Editors:
Cocks P. Large eddy simulation of supersonic combustion with application to scramjet engines. [Doctoral Dissertation]. University of Cambridge; 2011. Available from: https://doi.org/10.17863/CAM.14003 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541905
University of Cambridge
27.
Cocks, Peter.
Large eddy simulation of supersonic combustion with application to scramjet engines.
Degree: PhD, 2011, University of Cambridge
URL: http://www.dspace.cam.ac.uk/handle/1810/239344https://www.repository.cam.ac.uk/bitstream/1810/239344/2/license.txt
;
https://www.repository.cam.ac.uk/bitstream/1810/239344/5/thesis.pdf.txt
;
https://www.repository.cam.ac.uk/bitstream/1810/239344/6/thesis.pdf.jpg
► This work evaluates the capabilities of the RANS and LES techniques for the simulation of high speed reacting flows. These methods are used to gain…
(more)
▼ This work evaluates the capabilities of the RANS and LES techniques for the simulation of high speed reacting flows. These methods are used to gain further insight into the physics encountered and regimes present in supersonic combustion. The target application of this research is the scramjet engine, a propulsion system of great promise for efficient hypersonic flight. In order to conduct this work a new highly parallelised code, PULSAR, is developed. PULSAR is capable of simulating complex chemistry combustion in highly compressible flows, based on a second order upwind method to provide a monotonic solution in the presence of high gradient physics.
Through the simulation of a non-reacting supersonic coaxial helium jet the RANS method is shown to be sensitive to constants involved in the modelling process. The LES technique is more computationally demanding but is shown to be much less sensitive to these model parameters. Nevertheless, LES results are shown to be sensitive to the nature of turbulence at the inflow; however this information can be experimentally obtained.
The SCHOLAR test case is used to validate the reacting aspects of PULSAR. Comparing RANS results from laminar chemistry and assumed PDF combustion model simulations, the influence of turbulence-chemistry interactions in supersonic combustion is shown to be small. In the presence of reactions, the RANS results are sensitive to inflow turbulence, due to its influence on mixing. From complex chemistry simulations the combustion behaviour is evaluated to sit between the flamelet and distributed reaction regimes. LES results allow an evaluation of the physics involved, with a pair of coherent vortices identified as the dominant influence on mixing for the oblique wall fuel injection method. It is shown that inflow turbulence has a significant impact on the behaviour of these vortices and hence it is vital for turbulence intensities and length scales to be measured by experimentalists, in order for accurate simulations to be possible.
Subjects/Keywords: Scramjet; Supersonic combustion; Assumed pdf combustion model; Large eddy simulation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Cocks, P. (2011). Large eddy simulation of supersonic combustion with application to scramjet engines. (Doctoral Dissertation). University of Cambridge. Retrieved from http://www.dspace.cam.ac.uk/handle/1810/239344https://www.repository.cam.ac.uk/bitstream/1810/239344/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/239344/5/thesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/239344/6/thesis.pdf.jpg
Chicago Manual of Style (16th Edition):
Cocks, Peter. “Large eddy simulation of supersonic combustion with application to scramjet engines.” 2011. Doctoral Dissertation, University of Cambridge. Accessed February 27, 2021.
http://www.dspace.cam.ac.uk/handle/1810/239344https://www.repository.cam.ac.uk/bitstream/1810/239344/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/239344/5/thesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/239344/6/thesis.pdf.jpg.
MLA Handbook (7th Edition):
Cocks, Peter. “Large eddy simulation of supersonic combustion with application to scramjet engines.” 2011. Web. 27 Feb 2021.
Vancouver:
Cocks P. Large eddy simulation of supersonic combustion with application to scramjet engines. [Internet] [Doctoral dissertation]. University of Cambridge; 2011. [cited 2021 Feb 27].
Available from: http://www.dspace.cam.ac.uk/handle/1810/239344https://www.repository.cam.ac.uk/bitstream/1810/239344/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/239344/5/thesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/239344/6/thesis.pdf.jpg.
Council of Science Editors:
Cocks P. Large eddy simulation of supersonic combustion with application to scramjet engines. [Doctoral Dissertation]. University of Cambridge; 2011. Available from: http://www.dspace.cam.ac.uk/handle/1810/239344https://www.repository.cam.ac.uk/bitstream/1810/239344/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/239344/5/thesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/239344/6/thesis.pdf.jpg
University of Cambridge
28.
Langella, Ivan.
Large eddy simulation of premixed combustion using flamelets.
Degree: PhD, 2016, University of Cambridge
URL: https://www.repository.cam.ac.uk/handle/1810/254303https://www.repository.cam.ac.uk/bitstream/1810/254303/2/license.txt
;
https://www.repository.cam.ac.uk/bitstream/1810/254303/3/license_rdf
;
https://www.repository.cam.ac.uk/bitstream/1810/254303/4/PhDthesis.pdf.txt
;
https://www.repository.cam.ac.uk/bitstream/1810/254303/5/PhDthesis.pdf.jpg
► Large Eddy Simulation (LES) has potential to address unsteady phenomena in turbulent premixed flames and to capture turbulence scales and their influence on combustion. Thus,…
(more)
▼ Large Eddy Simulation (LES) has potential to address unsteady phenomena in turbulent premixed flames and to capture turbulence scales and their influence on combustion. Thus, this approach is gaining interest in industry to analyse turbulent reacting flows. In LES, the dynamics of large-scale turbulent eddies down to a cut-off scale are solved, with models to mimic the influences of sub-grid scales. Since the flame front is thinner than the smallest scale resolved in a typical LES, the premixed combustion is a sub-grid scale (SGS) phenomenon and involves strong interplay among small-scale turbulence, chemical reactions and molecular diffusion. Sub-grid scale combustion models must accurately represent these processes.
When the flame front is thinner than the smallest turbulent scale, the flame is corrugated by the turbulence and can be seen as an ensemble of thin, one-dimensional laminar flames (flamelets). This allows one to decouple turbulence from chemistry, with a significant reduction in computational effort. However, potentials and limitations of flamelets are not fully explored
and understood. This work contributes to this understanding. Two models are identified, one based on an algebraic expression for the reaction rate of a progress variable and the assumption of fast chemistry, the other based on a database of unstrained flamelets in which reaction rates are stored and parametrised using a progress variable and its SGS variance, and their potentials are shown for a wide range of premixed combustion conditions of practical interest. The sensitivity to a number of model parameters and boundary conditions is explored to assess the robustness of these models. This work shows that the SGS variance of progress variable plays a crucial role in the SGS reaction rate modelling and cannot be obtained using a simple algebraic closure like that commonly used for a passive scalar. The use of strained flamelets to include the flame stretching effects is not required when the variance is obtained from its transport equation and the resolved turbulence contains predominant part of the turbulent kinetic energy. Thus, it seems that SGS closure using unstrained flamelets model is robust and adequate for wide range of turbulent premixed combustion conditions.
Subjects/Keywords: premixed combustion; turbulence; computational fluid dynamics; large eddy simulation; flamelet models
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Langella, I. (2016). Large eddy simulation of premixed combustion using flamelets. (Doctoral Dissertation). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/254303https://www.repository.cam.ac.uk/bitstream/1810/254303/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/254303/3/license_rdf ; https://www.repository.cam.ac.uk/bitstream/1810/254303/4/PhDthesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/254303/5/PhDthesis.pdf.jpg
Chicago Manual of Style (16th Edition):
Langella, Ivan. “Large eddy simulation of premixed combustion using flamelets.” 2016. Doctoral Dissertation, University of Cambridge. Accessed February 27, 2021.
https://www.repository.cam.ac.uk/handle/1810/254303https://www.repository.cam.ac.uk/bitstream/1810/254303/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/254303/3/license_rdf ; https://www.repository.cam.ac.uk/bitstream/1810/254303/4/PhDthesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/254303/5/PhDthesis.pdf.jpg.
MLA Handbook (7th Edition):
Langella, Ivan. “Large eddy simulation of premixed combustion using flamelets.” 2016. Web. 27 Feb 2021.
Vancouver:
Langella I. Large eddy simulation of premixed combustion using flamelets. [Internet] [Doctoral dissertation]. University of Cambridge; 2016. [cited 2021 Feb 27].
Available from: https://www.repository.cam.ac.uk/handle/1810/254303https://www.repository.cam.ac.uk/bitstream/1810/254303/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/254303/3/license_rdf ; https://www.repository.cam.ac.uk/bitstream/1810/254303/4/PhDthesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/254303/5/PhDthesis.pdf.jpg.
Council of Science Editors:
Langella I. Large eddy simulation of premixed combustion using flamelets. [Doctoral Dissertation]. University of Cambridge; 2016. Available from: https://www.repository.cam.ac.uk/handle/1810/254303https://www.repository.cam.ac.uk/bitstream/1810/254303/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/254303/3/license_rdf ; https://www.repository.cam.ac.uk/bitstream/1810/254303/4/PhDthesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/254303/5/PhDthesis.pdf.jpg
University of Colorado
29.
Mazzaro, Laura Jin.
Mesoscale-To-Les Coupling of Atmospheric Boundary Layer Flows.
Degree: PhD, 2019, University of Colorado
URL: https://scholar.colorado.edu/atoc_gradetds/87
► The accurate simulation of multi-scale atmospheric processes is crucial for applications such as weather forecasting, flow over complex terrain and wind-energy prediction. However, coupling…
(more)
▼ The accurate
simulation of multi-scale atmospheric processes is crucial for applications such as weather forecasting, flow over complex terrain and wind-energy prediction. However, coupling between mesoscale models and microscale models can present many challenges. In this work we explore some of these challenges, and propose a new solution. First, we evaluate the effects of unrealistic, mesoscale structures affecting nested
large eddy simulations (LES) through boundary conditions, in the case of an idealized, convective boundary layer. Such unrealistic structures result from using mesoscale models at resolutions within a range known as the Terra Incognita (TI) (Wyngaard, 2004). From this analysis we find that unrealistic structures delay the generation of turbulence. However, after a proper turbulence-generation fetch, the LES simulations overcome the influence of the unrealistic structures and develop accurate turbulence. In the second part of this work, we implement and test a stochastic method for turbulence generation based on the cell perturbation method (CPM) (Munoz-Esparza et al., 2015; Munoz- Esparza and Kosovic, 2018) using the Weather Research and Forecasting model (WRF) Skamarock et al. (2008). This new method uses random vertical and horizontal force perturbations (FCPM) to trigger turbulent motions near the inflow boundaries of LES nested within mesoscale simulations. Tests under idealized convective and neutral stability conditions show that the FCPM can produce a comparable turbulence generation fetch to the CPM, pointing to the robustness of family of random perturbation methods. Vertical force perturbations were found to perform better than horizontal force perturbations for both convective, and neutral stability conditions. Finally, the third part of this work tests the new FCPM for the case of a real, diurnal cycle over flat terrain. Wind-speed measurements from a meteorological tower in the Scaled Wind Farm Technology (SWiFT) facility are used to validate the model performance. The FCPM produces closer mean flows to the tower measurements. The FCPM was able to produce turbulent motions during stable atmospheric conditions, while such motions were not produced by the unperturbed model. Additionally, the use of the FCPM was found to accelerate the development of turbulence to a fetch of up to 2.2 km, while the unperturbed case required up to 5.9 km to develop the equivalent scales.
Advisors/Committee Members: Julie J. Lundquist, Branko Kosovic, Peter Hamlington, Domingo Munoz-Esparza, John Cassano.
Subjects/Keywords: large eddy simulations; turbulence; atmospheric conditions; atmospheric processes; simulation; Atmospheric Sciences
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Mazzaro, L. J. (2019). Mesoscale-To-Les Coupling of Atmospheric Boundary Layer Flows. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/atoc_gradetds/87
Chicago Manual of Style (16th Edition):
Mazzaro, Laura Jin. “Mesoscale-To-Les Coupling of Atmospheric Boundary Layer Flows.” 2019. Doctoral Dissertation, University of Colorado. Accessed February 27, 2021.
https://scholar.colorado.edu/atoc_gradetds/87.
MLA Handbook (7th Edition):
Mazzaro, Laura Jin. “Mesoscale-To-Les Coupling of Atmospheric Boundary Layer Flows.” 2019. Web. 27 Feb 2021.
Vancouver:
Mazzaro LJ. Mesoscale-To-Les Coupling of Atmospheric Boundary Layer Flows. [Internet] [Doctoral dissertation]. University of Colorado; 2019. [cited 2021 Feb 27].
Available from: https://scholar.colorado.edu/atoc_gradetds/87.
Council of Science Editors:
Mazzaro LJ. Mesoscale-To-Les Coupling of Atmospheric Boundary Layer Flows. [Doctoral Dissertation]. University of Colorado; 2019. Available from: https://scholar.colorado.edu/atoc_gradetds/87
University of California – Berkeley
30.
Bao, Jingyi.
An improved immersed boundary method for atmospheric boundary layer simulations over complex terrain.
Degree: Civil and Environmental Engineering, 2018, University of California – Berkeley
URL: http://www.escholarship.org/uc/item/3md4n2dg
► Accurately simulating flow over complex terrain has long been a challenging scientific problem.As computational power increases, atmospheric simulations are pushed toward higher resolutions with enough…
(more)
▼ Accurately simulating flow over complex terrain has long been a challenging scientific problem.As computational power increases, atmospheric simulations are pushed toward higher resolutions with enough computational resources to better resolve complex topography. Turbulence and flow dynamics which decades ago could not be resolved (e.g. drainage flow over a steep mountain) can now be studied using computational tools. The Weather Research and Forecasting (WRF) model is a numerical weather prediction and atmospheric research model that can be used in a wide range of grid resolutions from mesoscale weather prediction (km scale) to large-eddy simulation for atmospheric boundary layer studies (∼100 m and finer scales). The WRF model uses terrain-following coordinates, which is adequate for mesoscale models where the details of the terrain are not well resolved and the terrain slope is not very steep. With increased resolution, resolved terrain slopes become steeper, and the native terrain-following coordinates used in WRF result in numerical errors and instability. To eliminate these numerical errors and instability, but still be able to use WRF’s grid nesting strategy to include weather effects for complex terrain simulation, an immersed boundary method was implemented into WRF by Lundquist et al. (2010, 2012). The immersed boundary method uses a non-conforming grid where the terrain surface is immersed into the grid. The immersed boundary conditions are enforced by adding an additional forcing term to the Navier-Stoke equations for the points near the immersed boundary. The original immersed boundary method in WRF-IBM uses a no-slip boundary condition, which is suitable for urban simulations with fine resolution (1 m). The no-slip boundary condition is not appropriate for atmospheric simulations at 100 m scale, where the surface layer and the underlying topography are not extremely well resolved.This dissertation focuses on the development of improved log-law boundary conditions forWRF-IBM to enable atmospheric simulations over complex terrain at horizontal resolutions on the order of 100 m. First an existing velocity-reconstruction immersed boundary method (VR-IBM)is implemented into WRF. The VR-IBM is tested extensively for flat terrain, an idealized hill, and flow over Askervein Hill. At very fine resolutions, VR-IBM performs well, but further tests show some limitations at intermediate resolutions, where VR-IBM for example develops spatial1oscillations. Other limitations are found for VR-IBM and another shear-stress reconstruction (SR-IBM) approach depending on resolution and grid aspect ratios (see also Arthur et al., 2019). Next, a new hybrid log-law boundary condition for IBM (HYBRID-IBM) is developed and implemented into WRF. This hybrid method is evaluated against VR-IBM and SR-IBM for a wide range of idealized cases (both flat terrain and idealized 3D hill at different slopes and resolutions) and real cases, including Askervein hill…
Subjects/Keywords: Environmental engineering; Complex terrain; Immersed boundary method; Large eddy simulation; WRF
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Bao, J. (2018). An improved immersed boundary method for atmospheric boundary layer simulations over complex terrain. (Thesis). University of California – Berkeley. Retrieved from http://www.escholarship.org/uc/item/3md4n2dg
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Bao, Jingyi. “An improved immersed boundary method for atmospheric boundary layer simulations over complex terrain.” 2018. Thesis, University of California – Berkeley. Accessed February 27, 2021.
http://www.escholarship.org/uc/item/3md4n2dg.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Bao, Jingyi. “An improved immersed boundary method for atmospheric boundary layer simulations over complex terrain.” 2018. Web. 27 Feb 2021.
Vancouver:
Bao J. An improved immersed boundary method for atmospheric boundary layer simulations over complex terrain. [Internet] [Thesis]. University of California – Berkeley; 2018. [cited 2021 Feb 27].
Available from: http://www.escholarship.org/uc/item/3md4n2dg.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Bao J. An improved immersed boundary method for atmospheric boundary layer simulations over complex terrain. [Thesis]. University of California – Berkeley; 2018. Available from: http://www.escholarship.org/uc/item/3md4n2dg
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
◁ [1] [2] [3] [4] [5] … [20] ▶
. 
Open Access Theses and Dissertations
