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University of Notre Dame
1.
Anne L Tufts.
Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>.
Degree: PhD, 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
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APA (6th Edition):
Tufts, A. L. (2018). Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>. (Doctoral Dissertation). University of Notre Dame. Retrieved from https://curate.nd.edu/show/d217qn62j1g
Chicago Manual of Style (16th Edition):
Tufts, Anne L. “Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>.” 2018. Doctoral Dissertation, University of Notre Dame. Accessed September 22, 2019.
https://curate.nd.edu/show/d217qn62j1g.
MLA Handbook (7th Edition):
Tufts, Anne L. “Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>.” 2018. Web. 22 Sep 2019.
Vancouver:
Tufts AL. Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>. [Internet] [Doctoral dissertation]. University of Notre Dame; 2018. [cited 2019 Sep 22].
Available from: https://curate.nd.edu/show/d217qn62j1g.
Council of Science Editors:
Tufts AL. Numerical Investigation of Sound Generation by Airfoil
Interaction with a Turbulent Shear Layer</h1>. [Doctoral Dissertation]. University of Notre Dame; 2018. Available from: https://curate.nd.edu/show/d217qn62j1g
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
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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 September 22, 2019.
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. 22 Sep 2019.
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 2019 Sep 22].
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
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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 September 22, 2019.
http://hdl.handle.net/10251/37345.
MLA Handbook (7th Edition):
Mompó Laborda, Juan Manuel. “Engineering Large Eddy Simulation of Diesel Sprays
.” 2014. Web. 22 Sep 2019.
Vancouver:
Mompó Laborda JM. Engineering Large Eddy Simulation of Diesel Sprays
. [Internet] [Doctoral dissertation]. Universitat Politècnica de València; 2014. [cited 2019 Sep 22].
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
University of Saskatchewan
4.
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
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APA ·
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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 September 22, 2019.
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. 22 Sep 2019.
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 2019 Sep 22].
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
5.
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
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744338
► 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
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APA ·
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MLA ·
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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 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744338
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 September 22, 2019.
https://www.repository.cam.ac.uk/handle/1810/269850 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744338.
MLA Handbook (7th Edition):
Denby, Leif Christopher. “Using high-resolution modelling to improve the parameterisation of convection in a climate model.” 2017. Web. 22 Sep 2019.
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 2019 Sep 22].
Available from: https://www.repository.cam.ac.uk/handle/1810/269850 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744338.
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 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744338
University of Cambridge
6.
Denby, Leif Christopher.
Using high-resolution modelling to improve the parameterisation of convection in a climate model
.
Degree: 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
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Record Details
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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
. (Thesis). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/269850
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):
Denby, Leif Christopher. “Using high-resolution modelling to improve the parameterisation of convection in a climate model
.” 2017. Thesis, University of Cambridge. Accessed September 22, 2019.
https://www.repository.cam.ac.uk/handle/1810/269850.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Denby, Leif Christopher. “Using high-resolution modelling to improve the parameterisation of convection in a climate model
.” 2017. Web. 22 Sep 2019.
Vancouver:
Denby LC. Using high-resolution modelling to improve the parameterisation of convection in a climate model
. [Internet] [Thesis]. University of Cambridge; 2017. [cited 2019 Sep 22].
Available from: https://www.repository.cam.ac.uk/handle/1810/269850.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Denby LC. Using high-resolution modelling to improve the parameterisation of convection in a climate model
. [Thesis]. University of Cambridge; 2017. Available from: https://www.repository.cam.ac.uk/handle/1810/269850
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Cambridge
7.
Wilsby, Oscar.
Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number
.
Degree: 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
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Record Details
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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
. (Thesis). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/294622
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):
Wilsby, Oscar. “Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number
.” 2019. Thesis, University of Cambridge. Accessed September 22, 2019.
https://www.repository.cam.ac.uk/handle/1810/294622.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Wilsby, Oscar. “Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number
.” 2019. Web. 22 Sep 2019.
Vancouver:
Wilsby O. Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number
. [Internet] [Thesis]. University of Cambridge; 2019. [cited 2019 Sep 22].
Available from: https://www.repository.cam.ac.uk/handle/1810/294622.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Wilsby O. Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number
. [Thesis]. University of Cambridge; 2019. Available from: https://www.repository.cam.ac.uk/handle/1810/294622
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Virginia Tech
8.
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
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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 September 22, 2019.
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. 22 Sep 2019.
Vancouver:
Patil S. Large Eddy Simulations of high Reynolds number Complex Flows with Synthetic Inlet Turbulence. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2019 Sep 22].
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
9.
Fueyo Díaz, Norberto.
Modelización de la combustión de llamas turbulentas mediante la simulación de las Grandes Escalas.
Degree: 2011, Universidad de Zaragoza
URL: http://zaguan.unizar.es/record/4573
► En este trabajo se desarrolla una estrategia para el modelado de flujos reactivos basada en el uso de Linear Eddy Model (LEM) como modelo submalla…
(more)
▼ En este trabajo se desarrolla una estrategia para el modelado de flujos reactivos basada en el uso de Linear Eddy Model (LEM) como modelo submalla en Simulaciones de las Grandes Escalas (LES). En la investigación se emplean las llamas turbulentas experimentales C, D y E de los laboratorios Sandía. El documento revisa concisamente el estado del arte de LES y las principales estrategias para el modelado de los flujos turbulentos reactivos. En la investigación se ha recurrido primero al modelo de flamelets estacionario. LEM se ha acoplado para modelar la evolución de escalares no reactivos y posteriormente como modelo de combustión. La información submalla del campo de escalares, principalmente la tasa de disipación, se analiza y compara con los datos experimentales. Los resultados concuerdan razonablemente con las mediciones por lo que se puede concluir que el modelo desarrollado captura adecuadamente las interacciones entre la cinética química y la turbulencia.
Subjects/Keywords: Large Eddy Simulation; Linear Eddy model; combustion; Computational Fluid Dynamics
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APA (6th Edition):
Fueyo Díaz, N. (2011). Modelización de la combustión de llamas turbulentas mediante la simulación de las Grandes Escalas. (Thesis). Universidad de Zaragoza. Retrieved from http://zaguan.unizar.es/record/4573
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):
Fueyo Díaz, Norberto. “Modelización de la combustión de llamas turbulentas mediante la simulación de las Grandes Escalas.” 2011. Thesis, Universidad de Zaragoza. Accessed September 22, 2019.
http://zaguan.unizar.es/record/4573.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Fueyo Díaz, Norberto. “Modelización de la combustión de llamas turbulentas mediante la simulación de las Grandes Escalas.” 2011. Web. 22 Sep 2019.
Vancouver:
Fueyo Díaz N. Modelización de la combustión de llamas turbulentas mediante la simulación de las Grandes Escalas. [Internet] [Thesis]. Universidad de Zaragoza; 2011. [cited 2019 Sep 22].
Available from: http://zaguan.unizar.es/record/4573.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Fueyo Díaz N. Modelización de la combustión de llamas turbulentas mediante la simulación de las Grandes Escalas. [Thesis]. Universidad de Zaragoza; 2011. Available from: http://zaguan.unizar.es/record/4573
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Minnesota
10.
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
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APA ·
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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 September 22, 2019.
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. 22 Sep 2019.
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 2019 Sep 22].
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
University of Colorado
11.
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
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APA ·
Chicago ·
MLA ·
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CSE |
Export
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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 September 22, 2019.
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. 22 Sep 2019.
Vancouver:
Coley CJ. Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2019 Sep 22].
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
Virginia Tech
12.
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
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APA ·
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MLA ·
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Export
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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 September 22, 2019.
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. 22 Sep 2019.
Vancouver:
Dilip D. Wall Modeled Large Eddy Simulation of Flow over a Wall Mounted Hump. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2019 Sep 22].
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
Brno University of Technology
13.
Volavý, Jaroslav.
Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation
.
Degree: 2013, Brno University of Technology
URL: http://hdl.handle.net/11012/28003
► Disertační práce se věnuje problematice numerických simulací vícefázového proudění, zvláště pak predikci pohybu disperzní fáze (částic) unášené proudem. Pro popis pohybu systému tekutina-částice je použit…
(more)
▼ Disertační práce se věnuje problematice numerických simulací vícefázového proudění, zvláště pak predikci pohybu disperzní fáze (částic) unášené proudem. Pro popis pohybu systému tekutina-částice je použit Euler-Lagrangeův přístup. To znamená, že tekutina je považována za kontinuum a pro popis jejího pohybu je použit Eulerův přístup, zatímco částice jsou uvažovány jako hmotné body a jejich pohyb je popsán pomocí přístupu Lagrangeova. Pro vyřešení pohybu nosné fáze je použita moderní metoda
Large Eddy Simulation. Byla provedena série simulací zpětného proudu za schodem s částicemi a byla sledována modulace turbulence částicemi. Koncentrace částic v~proudu je dostatečně vysoká, aby se projevil vliv částic na nosný proud. Turbulence na vstupu do domény je reprezentována pomocí vyvinutého schématu pro generaci turbulence na vstupu. Dále je v práci zkoumán vliv anizotropního rozkladu subgridní energie na pohyb částic.; 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).
Subjects/Keywords: Large Eddy Simulation;
turbulence na vstupu;
dvoufázové proudění;
modulace turbulence;
Large Eddy Simulation;
inlet boundary condition;
two-phase flow;
turbulence modulation
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❌
APA ·
Chicago ·
MLA ·
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CSE |
Export
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Manager
APA (6th Edition):
Volavý, J. (2013). Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation
. (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
.” 2013. Thesis, Brno University of Technology. Accessed September 22, 2019.
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
.” 2013. Web. 22 Sep 2019.
Vancouver:
Volavý J. Řešení turbulentního dvoufázového proudění metodou Large Eddy Simulation
. [Internet] [Thesis]. Brno University of Technology; 2013. [cited 2019 Sep 22].
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
. [Thesis]. Brno University of Technology; 2013. 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
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/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
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❌
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 September 22, 2019.
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. 22 Sep 2019.
Vancouver:
Coley CJ. Residual-Based Large Eddy Simulation of Turbulent Flows Using Divergence-Conforming Discretizations. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2019 Sep 22].
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
Loughborough University
15.
Coates, Tim.
Numerical simulation of unconventional aero-engine exhaust systems for aircraft.
Degree: PhD, 2014, Loughborough University
URL: https://dspace.lboro.ac.uk/2134/16365
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.631629
► 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
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APA (6th Edition):
Coates, T. (2014). Numerical simulation of unconventional aero-engine exhaust systems for aircraft. (Doctoral Dissertation). Loughborough University. Retrieved from https://dspace.lboro.ac.uk/2134/16365 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.631629
Chicago Manual of Style (16th Edition):
Coates, Tim. “Numerical simulation of unconventional aero-engine exhaust systems for aircraft.” 2014. Doctoral Dissertation, Loughborough University. Accessed September 22, 2019.
https://dspace.lboro.ac.uk/2134/16365 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.631629.
MLA Handbook (7th Edition):
Coates, Tim. “Numerical simulation of unconventional aero-engine exhaust systems for aircraft.” 2014. Web. 22 Sep 2019.
Vancouver:
Coates T. Numerical simulation of unconventional aero-engine exhaust systems for aircraft. [Internet] [Doctoral dissertation]. Loughborough University; 2014. [cited 2019 Sep 22].
Available from: https://dspace.lboro.ac.uk/2134/16365 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.631629.
Council of Science Editors:
Coates T. Numerical simulation of unconventional aero-engine exhaust systems for aircraft. [Doctoral Dissertation]. Loughborough University; 2014. Available from: https://dspace.lboro.ac.uk/2134/16365 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.631629
16.
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
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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 September 22, 2019.
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. 22 Sep 2019.
Vancouver:
Graham JS. Turbulence simulations: multiscale modeling and data-intensive computing methodologies. [Internet] [Thesis]. Johns Hopkins University; 2014. [cited 2019 Sep 22].
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
Loughborough University
17.
Durrani, Faisal.
Using large eddy simulation to model buoyancy-driven natural ventilation.
Degree: PhD, 2013, Loughborough University
URL: https://dspace.lboro.ac.uk/2134/12488
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588037
► The use of Large Eddy Simulation (LES) for modelling air flows in buildings is a growing area of Computational Fluid Dynamics (CFD). Compared to traditional…
(more)
▼ The use of Large Eddy Simulation (LES) for modelling air flows in buildings is a growing area of Computational Fluid Dynamics (CFD). Compared to traditional CFD techniques, LES provides a more detailed approach to modelling turbulence in air. This offers the potential for more accurate modelling of low energy natural ventilation which is notoriously difficult to model using traditional CFD. Currently, very little is known about the performance of LES for modelling natural ventilation, and its computational intensity makes its practical use on desk top computers prohibitive. The objective of this work was to apply LES to a variety of natural ventilation strategies and to compile guidelines for practitioners on its performance, including the trade-off between accuracy and cost.
Subjects/Keywords: 697.9; Large eddy simulation; Natural ventilation; Buoyancy; CFD; RANS; URANS
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Export
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APA (6th Edition):
Durrani, F. (2013). Using large eddy simulation to model buoyancy-driven natural ventilation. (Doctoral Dissertation). Loughborough University. Retrieved from https://dspace.lboro.ac.uk/2134/12488 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588037
Chicago Manual of Style (16th Edition):
Durrani, Faisal. “Using large eddy simulation to model buoyancy-driven natural ventilation.” 2013. Doctoral Dissertation, Loughborough University. Accessed September 22, 2019.
https://dspace.lboro.ac.uk/2134/12488 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588037.
MLA Handbook (7th Edition):
Durrani, Faisal. “Using large eddy simulation to model buoyancy-driven natural ventilation.” 2013. Web. 22 Sep 2019.
Vancouver:
Durrani F. Using large eddy simulation to model buoyancy-driven natural ventilation. [Internet] [Doctoral dissertation]. Loughborough University; 2013. [cited 2019 Sep 22].
Available from: https://dspace.lboro.ac.uk/2134/12488 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588037.
Council of Science Editors:
Durrani F. Using large eddy simulation to model buoyancy-driven natural ventilation. [Doctoral Dissertation]. Loughborough University; 2013. Available from: https://dspace.lboro.ac.uk/2134/12488 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588037
University of Utah
18.
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
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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 September 22, 2019.
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. 22 Sep 2019.
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 2019 Sep 22].
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
19.
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
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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 September 22, 2019.
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. 22 Sep 2019.
Vancouver:
Majander P. Large-Eddy Simulation of a Round Jet in a Cross-Flow. [Internet] [Thesis]. Helsinki University of Technology; 2006. [cited 2019 Sep 22].
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
University of Kansas
20.
McMichael, Lucas.
ASSESSING THE MECHANISMS GOVERNING THE DAYTIME EVOLUTION OF MARINE STRATOCUMULUS USING LARGE-EDDY SIMULATION.
Degree: MS, Geography, 2017, University of Kansas
URL: http://hdl.handle.net/1808/26986
► The individual mechanisms responsible for governing the evolution of afternoon cloud properties were explored for a case of thin stratocumulus off the coast of California…
(more)
▼ The individual mechanisms responsible for governing the evolution of afternoon cloud properties were explored for a case of thin stratocumulus off the coast of California by applying mixed-layer theory to
Large-
Eddy Simulation (LES) output. The development of a cloud-base tendency equation permitted the determination of the relative importance of mechanisms governing the evolution of boundary-layer liquid-water static energy () and total water mixing ratio (). The Control
simulation performed admirably in comparison to observed estimates of liquid water content, vertical velocity variance, and radiative fluxes sampled by the CIRPAS Twin Otter aircraft. The cloud response to various environmental forcing scenarios was investigated through a suite of sensitivity tests, including variations in subsidence velocity, temperature/moisture tendencies, surface fluxes, wind shear near the inversion, and radiative forcing. In the Control
simulation, rising cloud-base tendencies were related to entrainment warming and drying and shortwave absorption, while lowering cloud-base tendencies were associated with longwave cooling. Although there was substantial solar heating during the afternoon, the entrainment fluxes remained active throughout the analysis period. A reversal of cloud-base tendency was often observed in the simulations, as the reduction in shortwave warming later in the afternoon allowed for the recovery of the cloud. The evolution of cloud-base tendency is found to be insensitive to the net radiative flux divergence for most of the simulations (LWP ranging from ~10-50 g m-2). Error analysis suggests our method of entrainment flux calculation could be improved by a more complete understanding of entrainment layer physics.
Advisors/Committee Members: Mechem, David B (advisor), Rahn, David A (cmtemember), Braaten, David A (cmtemember).
Subjects/Keywords: Atmospheric sciences; Eddy; Large; Layer; Mixed; Simulation; Stratocumulus
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APA (6th Edition):
McMichael, L. (2017). ASSESSING THE MECHANISMS GOVERNING THE DAYTIME EVOLUTION OF MARINE STRATOCUMULUS USING LARGE-EDDY SIMULATION. (Masters Thesis). University of Kansas. Retrieved from http://hdl.handle.net/1808/26986
Chicago Manual of Style (16th Edition):
McMichael, Lucas. “ASSESSING THE MECHANISMS GOVERNING THE DAYTIME EVOLUTION OF MARINE STRATOCUMULUS USING LARGE-EDDY SIMULATION.” 2017. Masters Thesis, University of Kansas. Accessed September 22, 2019.
http://hdl.handle.net/1808/26986.
MLA Handbook (7th Edition):
McMichael, Lucas. “ASSESSING THE MECHANISMS GOVERNING THE DAYTIME EVOLUTION OF MARINE STRATOCUMULUS USING LARGE-EDDY SIMULATION.” 2017. Web. 22 Sep 2019.
Vancouver:
McMichael L. ASSESSING THE MECHANISMS GOVERNING THE DAYTIME EVOLUTION OF MARINE STRATOCUMULUS USING LARGE-EDDY SIMULATION. [Internet] [Masters thesis]. University of Kansas; 2017. [cited 2019 Sep 22].
Available from: http://hdl.handle.net/1808/26986.
Council of Science Editors:
McMichael L. ASSESSING THE MECHANISMS GOVERNING THE DAYTIME EVOLUTION OF MARINE STRATOCUMULUS USING LARGE-EDDY SIMULATION. [Masters Thesis]. University of Kansas; 2017. Available from: http://hdl.handle.net/1808/26986
University of Cincinnati
21.
POONDRU, SHIRDISH.
Large-Eddy Simulation and Active Flow Control of
Low-Reynolds Number Flow through a Low-Pressure Turbine
Cascade.
Degree: PhD, Engineering : Mechanical Engineering, 2008, University of Cincinnati
URL: http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204873699
► The operating Reynolds numbers (Re) for a low-pressure turbine (LPT) in an aircraft engine can drop below 25,000 during high-altitude cruise conditions, resulting in…
(more)
▼ The operating Reynolds numbers (Re) for a
low-pressure turbine (LPT) in an aircraft engine can drop below
25,000 during high-altitude cruise conditions, resulting in massive
separation and subsequent transition on the blade suction surface.
This separation causes a significant loss in the engine efficiency.
Hence, accurate prediction of the flow physics at these low-Re
conditions is required to effectively implement flow control
techniques which can help mitigate separation-induced losses. The
present work investigated this low-Re transitional flow through a
LPT cascade comprised of the generic Pratt & Whitney “PAKB”
blades, using high-order accurate compact numerical schemes in
conjunction with
large-
eddy simulation (LES), with and without
subgrid-scale (SGS) models. The study examined the predictive
capability of the explicit Smagorinsky and dynamic Smagorinsky SGS
models, as compared to the Implicit LES (ILES) technique (LES
without an explicit SGS model). The research also implemented
active flow control on the LPT blades using momentum injection via
surface blowing. All simulations utilized a dual-topology,
multi-block, structured grid, and computations were performed on a
massively parallel computing platform using MPI-based
communications. The baseline cases (without control) were simulated
at Re ~ 10,000, 25,000 and 50,000. The computed numerical results
for all three cases showed good agreement with available
experimental data. The Smagorinsky and dynamic Smagorinsky SGS
model results provided no significant improvement over the ILES
results because of the low level of energy in the subgrid-scales
for the present low-Re flow conditions investigated, and hence, the
ILES technique was used for all subsequent flow-control
simulations. Separation control of the LPT flow
was implemented using synthetic normal jets, synthetic
vortex-generator jets, and pulsed vortex-generator jets (VGJs) at
Re ~ 10,000, for four blowing ratios ranging from 0.5 to 4.7, where
the blowing ratio is defined as the ratio of the jet-exit velocity
magnitude to the local free-stream velocity. All the jets were
implemented by specifying an analytical boundary condition at the
jet exit surface. The effectiveness of the jets was assessed in
terms of the integrated wake loss coefficient values, and the
modified Zweifel coefficient values. The Zweifel coefficient
represents the component of the integrated blade Cp distribution
contributing to the direction of rotation. Among the three types of
control jets implemented, the synthetic normal jets were found to
be more effective than the synthetic or pulsed VGJs. For pulsed
VGJs, the effective blowing ratio was found to be 2.0 in the
present study, compared to the value of 0.4 documented in the
literature for control at a Re = 25,000, indicating a strong
dependence of the effective blowing ratio on Re. The study also
examined the flow control mechanisms of the synthetic normal jets
and vortex-generator jets. It was found that the mechanism for
effectiveness of synthetic jets was a…
Advisors/Committee Members: Ghia, Urmila (Advisor).
Subjects/Keywords: Engineering, Mechanical; Large-eddy simulation; Low-pressure turbines; Active flow control
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APA (6th Edition):
POONDRU, S. (2008). Large-Eddy Simulation and Active Flow Control of
Low-Reynolds Number Flow through a Low-Pressure Turbine
Cascade. (Doctoral Dissertation). University of Cincinnati. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204873699
Chicago Manual of Style (16th Edition):
POONDRU, SHIRDISH. “Large-Eddy Simulation and Active Flow Control of
Low-Reynolds Number Flow through a Low-Pressure Turbine
Cascade.” 2008. Doctoral Dissertation, University of Cincinnati. Accessed September 22, 2019.
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204873699.
MLA Handbook (7th Edition):
POONDRU, SHIRDISH. “Large-Eddy Simulation and Active Flow Control of
Low-Reynolds Number Flow through a Low-Pressure Turbine
Cascade.” 2008. Web. 22 Sep 2019.
Vancouver:
POONDRU S. Large-Eddy Simulation and Active Flow Control of
Low-Reynolds Number Flow through a Low-Pressure Turbine
Cascade. [Internet] [Doctoral dissertation]. University of Cincinnati; 2008. [cited 2019 Sep 22].
Available from: http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204873699.
Council of Science Editors:
POONDRU S. Large-Eddy Simulation and Active Flow Control of
Low-Reynolds Number Flow through a Low-Pressure Turbine
Cascade. [Doctoral Dissertation]. University of Cincinnati; 2008. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204873699
University of Exeter
22.
Taylor, Alexander Charles.
Dispersion by time-varying atmospheric boundary layers.
Degree: PhD, 2012, University of Exeter
URL: http://hdl.handle.net/10036/3602
► The periods of time-varying turbulence in the atmospheric boundary layer, i.e. the morning and evening transitions, are often overlooked or highly idealised by dispersion models.…
(more)
▼ The periods of time-varying turbulence in the atmospheric boundary layer, i.e. the morning and evening transitions, are often overlooked or highly idealised by dispersion models. These transitions make up a significant portion of the diurnal cycle and are known to affect the spread of pollution due to the properties of turbulence in the residual and stable layers, resulting in phenomena such as lofting, trapping, and fumigation.\ Two main simulation techniques are presented for the purpose of modelling the dispersion of passive tracers in both convective and evening transitional boundary layers: Lagrangian stochastic (LS) modelling for 1D, inhomogeneous, non-stationary turbulence; and large-eddy simulation (LES) with a particle model tracing pollutant paths using a combination of the resolved flow velocities and a random displacement model to represent sub-grid scale motions.\ In the convective boundary layer, LS models more accurately representing the state of turbulence, and including the effect of skewness, are shown to produce dispersion results in closer agreement with LES. By considering individual particle trajectories, a reflective top boundary in LS models is shown to produce un-physical, sharp changes in velocity and position. By applying a correction to the vertical velocity variance based on representing the stable potential temperature gradient above the boundary layer, particles are contained within the boundary layer in a physically accurate way. \ An LS model for predicting dispersion in time-varying, skewed turbulence is developed and tested for various particle releases in transitional boundary layers with different rates of decay, showing an improvement in accuracy compared with previous LS models. Further improvement is made by applying a correction to the vertical velocity variance to represent the effect of a positive potential temperature gradient developing over the course of the transition. Finally, a developing stable boundary layer is shown to have a significant trapping effect on particles released near the surface. \\
Subjects/Keywords: 551.515; Boundary layer, : large-eddy simulation : Largangian stochastic : pollution : transition : convective
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APA (6th Edition):
Taylor, A. C. (2012). Dispersion by time-varying atmospheric boundary layers. (Doctoral Dissertation). University of Exeter. Retrieved from http://hdl.handle.net/10036/3602
Chicago Manual of Style (16th Edition):
Taylor, Alexander Charles. “Dispersion by time-varying atmospheric boundary layers.” 2012. Doctoral Dissertation, University of Exeter. Accessed September 22, 2019.
http://hdl.handle.net/10036/3602.
MLA Handbook (7th Edition):
Taylor, Alexander Charles. “Dispersion by time-varying atmospheric boundary layers.” 2012. Web. 22 Sep 2019.
Vancouver:
Taylor AC. Dispersion by time-varying atmospheric boundary layers. [Internet] [Doctoral dissertation]. University of Exeter; 2012. [cited 2019 Sep 22].
Available from: http://hdl.handle.net/10036/3602.
Council of Science Editors:
Taylor AC. Dispersion by time-varying atmospheric boundary layers. [Doctoral Dissertation]. University of Exeter; 2012. Available from: http://hdl.handle.net/10036/3602
The Ohio State University
23.
Speth, Rachelle Lea.
Controlling The Development of Coherent Structures in High
Speed Jets and The Resultant Near Field.
Degree: PhD, Aero/Astro Engineering, 2015, The Ohio State University
URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1447419083
► This work uses Large-Eddy Simulations to examine the effect of actuator parameters and jet exit properties on the evolution of coherent structures and their impact…
(more)
▼ This work uses
Large-
Eddy Simulations to examine the
effect of actuator parameters and jet exit properties on the
evolution of coherent structures and their impact on the
near-acoustic field without and with control. For the controlled
cases, Localized Arc Filament Plasma Actuators (LAFPAs) are
considered, and modeled with a simple heating approach that
successfully reproduces the main observations and trends of
experiments.A parametric study is first conducted, using the
flapping mode (m=±1), to investigate the sensitivity of the results
to various actuator parameters including: actuator model
temperature, actuator duty cycle, and excitation frequency. It is
shown by considering a Mach 1.3 jet at Reynolds number of 1
×10
6 that the response of the jet is
relatively insensitive to actuator model temperature within the
limits of the experimentally measured temperature values.
Furthermore, duty cycles in the range of 20%-90% were observed to
be effective in reproducing the characteristic coherent structures
of the flapping mode. The 90% duty cycle exhibits strengthened
coherent structures and slightly higher jet growth along the
flapping plane, but the overall dynamics remain almost identical to
the lower duty cycle cases. However, a 100% duty cycle had no
perceptible effect on the jet. Therefore, increasing the energy
inserted into the flow via actuator temperature or duty cycle does
not significantly alter the flow dynamics. The largest sensitivity
was associated with excitation frequency, with the mostsignificant
effect associated with the column mode instability frequency (St
¿0.3), which results in alternating vortex rings for this mode.
Higher and lower frequencies reduced the rate of decay of
thecenterline velocity. Although the higher frequencies increased
the number of features observed in the phase-averaged data, their
prominence is reduced due to their breakdown into smaller
structures. These actuator parameter results confirm that the flow
response and control authority is associated with manipulation of
flow instability, rather than heat deposition.Next, jet flow
parameters were explored to determine the control authority under
different operating conditions. To begin, the effect of the laminar
nozzle exit boundary layer thickness was examined by varying its
value from essentially uniform flow to 25% of the diameter. In the
absence of control, the distance between the nozzle lip and the
initial appearance of breakdown is proportional to the
boundary-layer thickness, which is consistent with theory and
previous results obtained by other researchers at Mach 0.9.
However, the subsequent growth towards the centerline is faster for
the thicker boundary layers. For flapping mode control, increasing
the thickness of the boundary layer has different effects on the
flapping and non-flapping planes. The rapid spreading of the jet
observed on the flapping plane with thin boundary layers is greatly
diminished as the nozzle exit layer is thickened. Conversely, the
rate of spreading on the non-flapping plane…
Advisors/Committee Members: Gaitonde, Datta (Advisor).
Subjects/Keywords: Acoustics; Aerospace Engineering; acoustics; large eddy simulation; jets; plasma control
Record Details
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APA ·
Chicago ·
MLA ·
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Export
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Manager
APA (6th Edition):
Speth, R. L. (2015). Controlling The Development of Coherent Structures in High
Speed Jets and The Resultant Near Field. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1447419083
Chicago Manual of Style (16th Edition):
Speth, Rachelle Lea. “Controlling The Development of Coherent Structures in High
Speed Jets and The Resultant Near Field.” 2015. Doctoral Dissertation, The Ohio State University. Accessed September 22, 2019.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1447419083.
MLA Handbook (7th Edition):
Speth, Rachelle Lea. “Controlling The Development of Coherent Structures in High
Speed Jets and The Resultant Near Field.” 2015. Web. 22 Sep 2019.
Vancouver:
Speth RL. Controlling The Development of Coherent Structures in High
Speed Jets and The Resultant Near Field. [Internet] [Doctoral dissertation]. The Ohio State University; 2015. [cited 2019 Sep 22].
Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1447419083.
Council of Science Editors:
Speth RL. Controlling The Development of Coherent Structures in High
Speed Jets and The Resultant Near Field. [Doctoral Dissertation]. The Ohio State University; 2015. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1447419083
Penn State University
24.
Yang, Ning.
BLOOD FLOW IN END-TO-SIDE ANASTOMOSES OF VENTRICULAR ASSIST
DEVICES.
Degree: PhD, Bioengineering, 2009, Penn State University
URL: https://etda.libraries.psu.edu/catalog/10250
► Although there are many studies that focus on the fluid mechanics within ventricular assist devices (VADs), the impact of VAD anastomoses on the aortic flow…
(more)
▼ Although there are many studies that focus on the
fluid mechanics within ventricular assist devices (VADs), the
impact of VAD anastomoses on the aortic flow has been largely
ignored. Hence, we study the blood flow within the end-to-side
anastomoses of VADs to adult and pediatric aortas. The great
vessels originating from the aortic arch are included to study flow
splitting. A second-order accurate time-dependent flow solver based
on finite volume method is used to simulate the flow. Monotone
integrated large eddy simulation is used to resolve large scales of
the resulting turbulent flow based on grid cut-off and to model the
sub-grid scale (SGS) motions using non-linear built-in (implicit)
SGS turbulence models. Hemolysis is modeled using an
advection-reaction transport equation. The flow solver is validated
against analytical and experimental results. The effect of blood
viscoelasticity is examined experimentally using particle image
velocimentry. Our results suggest that the VAD anastomosis
significantly alters the flow in the aorta. A proximal anastomotic
configuration diverts an impingement jet into the brachiocephalic
artery and may increase the perioperative right-sided stroke rate,
whereas a distal anastomotic configuration leads to a large
stagnant flow region near the aortic valve and possible thrombosis.
Turbulence occurs for both configurations during the complete VAD
support. The continuous support significantly reduces the blood
damage in the aorta when compared to the pulsatile support,
although it could lead to end-organ failure as a result of the
reduced pulsatility. This work may help to identify the risk of
graft failure for patients with VAD assistance.
Subjects/Keywords: monotone integrated large eddy simulation; turbulence;
hemolysis; anastomosis; ventrciular assist device
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Yang, N. (2009). BLOOD FLOW IN END-TO-SIDE ANASTOMOSES OF VENTRICULAR ASSIST
DEVICES. (Doctoral Dissertation). Penn State University. Retrieved from https://etda.libraries.psu.edu/catalog/10250
Chicago Manual of Style (16th Edition):
Yang, Ning. “BLOOD FLOW IN END-TO-SIDE ANASTOMOSES OF VENTRICULAR ASSIST
DEVICES.” 2009. Doctoral Dissertation, Penn State University. Accessed September 22, 2019.
https://etda.libraries.psu.edu/catalog/10250.
MLA Handbook (7th Edition):
Yang, Ning. “BLOOD FLOW IN END-TO-SIDE ANASTOMOSES OF VENTRICULAR ASSIST
DEVICES.” 2009. Web. 22 Sep 2019.
Vancouver:
Yang N. BLOOD FLOW IN END-TO-SIDE ANASTOMOSES OF VENTRICULAR ASSIST
DEVICES. [Internet] [Doctoral dissertation]. Penn State University; 2009. [cited 2019 Sep 22].
Available from: https://etda.libraries.psu.edu/catalog/10250.
Council of Science Editors:
Yang N. BLOOD FLOW IN END-TO-SIDE ANASTOMOSES OF VENTRICULAR ASSIST
DEVICES. [Doctoral Dissertation]. Penn State University; 2009. Available from: https://etda.libraries.psu.edu/catalog/10250
Penn State University
25.
Salesky, Scott Thomas.
Similarity Models of Subfilter-Scale Energy and Temperature
Variance for Large Eddy Simulations of the Atmospheric Boundary
Layer.
Degree: MS, Meteorology, 2010, Penn State University
URL: https://etda.libraries.psu.edu/catalog/10770
► Knowledge of the subfilter-scale (SFS) energy is instrumental for several reasons in Large Eddy Simulations (LES) of the atmospheric boundary layer (ABL). The SFS energy…
(more)
▼ Knowledge of the subfilter-scale (SFS) energy is
instrumental for several reasons in Large Eddy Simulations (LES) of
the atmospheric boundary layer (ABL). The SFS energy must be known
to recover the true pressure field from the modified pressure used
in simulations and may be used to form an eddy viscosity to model
the SFS stress tensor. The SFS energy also must be known in LES of
compressible flow to close the set of governing equations. The
one-equation model, which determines the SFS energy through the
numerical solution of its rate equation, is frequently used in LES.
Although this approach is common, it has a high computational cost
and requires closure assumptions. Several alternative models for
the SFS energy have been proposed, including models formed by
dimensional analysis, others that assume a spectral shape which is
integrated to obtain the SFS energy, and others that are based on
the hypothesis of scale similarity. Many of these models are
strictly global, however, meaning that they can only predict the
average SFS energy. A local model is proposed for the SFS energy in
LES of the ABL that is based on the scale similarity between the
SFS energy and the trace of the Leonard stress tensor. The SFS
energy model is derived from a stability-dependent atmospheric
model of the energy spectrum that incorporates the effects of
buoyancy and shear and therefore can account for the shape of the
energy spectrum at low wavenumbers. Furthermore, this approach has
a lower computational cost than the one-equation model, since the
Leonard stress can be calculated easily in simulations. Results
from an a priori test using data from the Horizontal Array
Turbulence Study (HATS) demonstrate that the model performs well in
both a global and a local sense. The model is able to correctly
predict the average SFS energy for most stabilities and
dimensionless filter widths considered, and does so more accurately
than a similar model that assumes an infinite -5/3 energy spectrum.
The model also performs well in a local sense, producing a
probability distribution function (PDF) similar to that of the
actual SFS energy. This procedure is also extended to develop a
model for the SFS temperature variance.
Subjects/Keywords: SFS modeling; turbulence; atmospheric boundary layer;
large eddy simulation; SFS energy
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APA ·
Chicago ·
MLA ·
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CSE |
Export
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Manager
APA (6th Edition):
Salesky, S. T. (2010). Similarity Models of Subfilter-Scale Energy and Temperature
Variance for Large Eddy Simulations of the Atmospheric Boundary
Layer. (Masters Thesis). Penn State University. Retrieved from https://etda.libraries.psu.edu/catalog/10770
Chicago Manual of Style (16th Edition):
Salesky, Scott Thomas. “Similarity Models of Subfilter-Scale Energy and Temperature
Variance for Large Eddy Simulations of the Atmospheric Boundary
Layer.” 2010. Masters Thesis, Penn State University. Accessed September 22, 2019.
https://etda.libraries.psu.edu/catalog/10770.
MLA Handbook (7th Edition):
Salesky, Scott Thomas. “Similarity Models of Subfilter-Scale Energy and Temperature
Variance for Large Eddy Simulations of the Atmospheric Boundary
Layer.” 2010. Web. 22 Sep 2019.
Vancouver:
Salesky ST. Similarity Models of Subfilter-Scale Energy and Temperature
Variance for Large Eddy Simulations of the Atmospheric Boundary
Layer. [Internet] [Masters thesis]. Penn State University; 2010. [cited 2019 Sep 22].
Available from: https://etda.libraries.psu.edu/catalog/10770.
Council of Science Editors:
Salesky ST. Similarity Models of Subfilter-Scale Energy and Temperature
Variance for Large Eddy Simulations of the Atmospheric Boundary
Layer. [Masters Thesis]. Penn State University; 2010. Available from: https://etda.libraries.psu.edu/catalog/10770
26.
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
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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 September 22, 2019.
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. 22 Sep 2019.
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 2019 Sep 22].
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
Louisiana State University
27.
Agegnehu, Getnet Baynesagne.
Applications of Large Eddy Simulation to Study Flow and Sediment Transport in Open Channel Flows.
Degree: PhD, Civil and Environmental Engineering, 2015, Louisiana State University
URL: etd-06032015-000351
;
https://digitalcommons.lsu.edu/gradschool_dissertations/2684
► The motivation of this study is to extend applications of Large Eddy Simulation (LES) for typical open channel flows to elucidate the time dependent three…
(more)
▼ The motivation of this study is to extend applications of Large Eddy Simulation (LES) for typical open channel flows to elucidate the time dependent three dimensional flow and sediment transport features which are usually difficult to measure in experiments. Detailed investigations are performed on the unsteady features and, in particular, turbulent structures of the flow to demonstrate the great potential of eddy resolving methods. The instantaneous flow and sediment transport fields are investigated together with the existence of coherent structures. These structures together with ejection events (u' < 0, w' > 0), are responsible for the vertical and lateral transport of suspended sediment from the near bed region. Stronger velocity perturbation vectors are also observed around the coherent structures, demonstrating that these areas are highly dynamic zones of flow and sediment transport. As a result of the enhanced viscosity, sediment induced stratification, and particle pressure effects, a reduction on the peak turbulence levels is shown for both the wall normal and Reynolds shear stress components in the sediment concentrated recirculation and near-bed regions. These phenomena can potentially decrease the vertical mixing and turbulent suspension of sediment particles in the flow field. Three dimensional hydrodynamic simulations are also conducted for ~10 meter section of the Expanded Small Scale Physical Model (ESSPM) of the Lower Mississippi River to gain insights on the effects of model distortion on various hydrodynamic variables. Analysis and comparisons are carried out at two distortion scales (i.e., 15, the design distortion and 7.5) using turbulence resolving simulations. Overall, the difference in horizontal mean velocity profiles and velocity fluctuations from the two distortion levels is small, supporting the ability of a distorted models to replicate bulk 1-D sediment transport rates. The work presented in this dissertation demonstrates that LES is advantageous for solving the complex flow and sediment transport dynamics by resolving the large scale eddies of the turbulent motion and that, when coupled with a sediment transport model, will provide valuable insights into three dimensional turbulence-sediment interactions.
Subjects/Keywords: coherent structures; sediment transport; OpenFOAM; open channel flow; large eddy simulation
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Manager
APA (6th Edition):
Agegnehu, G. B. (2015). Applications of Large Eddy Simulation to Study Flow and Sediment Transport in Open Channel Flows. (Doctoral Dissertation). Louisiana State University. Retrieved from etd-06032015-000351 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2684
Chicago Manual of Style (16th Edition):
Agegnehu, Getnet Baynesagne. “Applications of Large Eddy Simulation to Study Flow and Sediment Transport in Open Channel Flows.” 2015. Doctoral Dissertation, Louisiana State University. Accessed September 22, 2019.
etd-06032015-000351 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2684.
MLA Handbook (7th Edition):
Agegnehu, Getnet Baynesagne. “Applications of Large Eddy Simulation to Study Flow and Sediment Transport in Open Channel Flows.” 2015. Web. 22 Sep 2019.
Vancouver:
Agegnehu GB. Applications of Large Eddy Simulation to Study Flow and Sediment Transport in Open Channel Flows. [Internet] [Doctoral dissertation]. Louisiana State University; 2015. [cited 2019 Sep 22].
Available from: etd-06032015-000351 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2684.
Council of Science Editors:
Agegnehu GB. Applications of Large Eddy Simulation to Study Flow and Sediment Transport in Open Channel Flows. [Doctoral Dissertation]. Louisiana State University; 2015. Available from: etd-06032015-000351 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2684
Louisiana State University
28.
Roy, Somnath.
Macroinstability and Perturbation in Turbulent Stirred Tank Flows.
Degree: PhD, Mechanical Engineering, 2010, Louisiana State University
URL: etd-04162010-155954
;
https://digitalcommons.lsu.edu/gradschool_dissertations/1534
► Impeller stirred tank reactors (STRs) are commonly used in the chemical processing industries for a variety of mixing and blending technologies. In this research, a…
(more)
▼ Impeller stirred tank reactors (STRs) are commonly used in the chemical processing industries for a variety of mixing and blending technologies. In this research, a numerical study of flow and mixing inside turbulently agitated STRs are carried out. An immersed boundary method (IBM) is utilized to represent moving impeller geometries in the background of multi-block structured curvilinear fluid. The IBM This curvilinear-IBM methodology is further combined with the large eddy simulation (LES) technique to address the issue of modeling unsteady turbulent flows in the STR. Verification of the combined IBM-LES implementation strategy in curvilinear coordinates is done through comparisons with the measurements of laminar and turbulent flows in baffled STRs with pitched blade impellers. Flow structures are studied inside a dished bottom pitched-blade baffled for different impeller rotational speeds in the turbulent regime to observe the formation of trailing edge vortices which are associated with higher levels of turbulent kinetic energy relative to the remaining flowfield. Instabilities occurring at a frequency lower than the frequency of impeller rotation are identified from the time signal of velocity components. The role of these low frequency macro-instabilities (MI) is explored by observing changes in the three-dimensional circulation pattern within the STR. Significant amount of kinetic energy is observed to be associated with the dynamics of the trailing edge vortices during MI cycles. Flow inside an unbaffled Rushton impeller STR is perturbed using time-dependent impeller rotational speeds at a dominant MI frequency. Perturbation increased the mean radial width of the impeller jet-stream and enhanced overall turbulent kinetic energy compared to the constant rotational speed cases. Large-scale periodic velocity fluctuations due to perturbations produced large strain rates favoring higher turbulence production. Fluctuations in power consumptions are shown to correlate with the perturbation amplitude. Study on the mixing of a passive scalar inside STR showed that the growth rate of unmixed tracer is influenced by the MI oscillations. Perturbation of the STR flow resulted into significant reduction of mixing time. The spatio-temporal behavior of the large-scale mixing structures revealed that fast mixing is promoted due to the break-up of unmixed segregated zones during a perturbation cycle.
Subjects/Keywords: Turbulence; Large-eddy Simulation; Macroinstability; Perturbation; Stirred Tank; Mixing
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APA ·
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MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Roy, S. (2010). Macroinstability and Perturbation in Turbulent Stirred Tank Flows. (Doctoral Dissertation). Louisiana State University. Retrieved from etd-04162010-155954 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1534
Chicago Manual of Style (16th Edition):
Roy, Somnath. “Macroinstability and Perturbation in Turbulent Stirred Tank Flows.” 2010. Doctoral Dissertation, Louisiana State University. Accessed September 22, 2019.
etd-04162010-155954 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1534.
MLA Handbook (7th Edition):
Roy, Somnath. “Macroinstability and Perturbation in Turbulent Stirred Tank Flows.” 2010. Web. 22 Sep 2019.
Vancouver:
Roy S. Macroinstability and Perturbation in Turbulent Stirred Tank Flows. [Internet] [Doctoral dissertation]. Louisiana State University; 2010. [cited 2019 Sep 22].
Available from: etd-04162010-155954 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1534.
Council of Science Editors:
Roy S. Macroinstability and Perturbation in Turbulent Stirred Tank Flows. [Doctoral Dissertation]. Louisiana State University; 2010. Available from: etd-04162010-155954 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1534
UCLA
29.
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
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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 September 22, 2019.
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. 22 Sep 2019.
Vancouver:
Amouyal S. Numerical simulation of a closed rotor-stator system using Large Eddy Simulation. [Internet] [Thesis]. UCLA; 2014. [cited 2019 Sep 22].
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 Saskatchewan
30.
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…
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▼ 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
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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 September 22, 2019.
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. 22 Sep 2019.
Vancouver:
Einian M. LARGE EDDY SIMULATION OF FLOW AROUND A FINITE SQUARE CYLINDER. [Internet] [Thesis]. University of Saskatchewan; 2012. [cited 2019 Sep 22].
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
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Open Access Theses and Dissertations