subject:(direct numerical simulation)

University of Melbourne

1. Kozul, Melissa. The turbulent boundary layer studied using novel numerical frameworks.

Degree: 2018, University of Melbourne

► Numerical simulation of turbulent boundary layers is a challenging task that has prompted the development of different numerical setups. To complement existing techniques, the temporal… (more)

Subjects/Keywords: turbulent boundary layers; direct numerical simulation

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APA (6^th Edition):

Kozul, M. (2018). The turbulent boundary layer studied using novel numerical frameworks. (Doctoral Dissertation). University of Melbourne. Retrieved from http://hdl.handle.net/11343/213493

Chicago Manual of Style (16^th Edition):

Kozul, Melissa. “The turbulent boundary layer studied using novel numerical frameworks.” 2018. Doctoral Dissertation, University of Melbourne. Accessed January 17, 2021. http://hdl.handle.net/11343/213493.

MLA Handbook (7^th Edition):

Kozul, Melissa. “The turbulent boundary layer studied using novel numerical frameworks.” 2018. Web. 17 Jan 2021.

Vancouver:

Kozul M. The turbulent boundary layer studied using novel numerical frameworks. [Internet] [Doctoral dissertation]. University of Melbourne; 2018. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11343/213493.

Council of Science Editors:

Kozul M. The turbulent boundary layer studied using novel numerical frameworks. [Doctoral Dissertation]. University of Melbourne; 2018. Available from: http://hdl.handle.net/11343/213493

Queens University

2. Bespalko, Dustin John. Validation of the Lattice Boltzmann Method for Direct Numerical Simulation of Wall-Bounded Turbulent Flows .

Degree: Mechanical and Materials Engineering, 2011, Queens University

URL: http://hdl.handle.net/1974/6729

► In this work, the lattice Boltzmann method (LBM) was validated for direct numerical simulation (DNS) of wall-bounded turbulent flows. The LBM is a discrete-particle-based method… (more)

▼ In this work, the lattice Boltzmann method (LBM) was validated for direct numerical simulation (DNS) of wall-bounded turbulent flows. The LBM is a discrete-particle-based method that numerically solves the Boltzmann equation as opposed to conventional DNS methods that are based on the Navier-Stokes (NS) equations. The advantages of the LBM are its simple implementation, its ability to handle complex geometries, and its scalability on modern high-performance computers. An LBM code was developed and used to simulate fully-developed turbulent channel flow. In order to validate the results, the turbulence statistics were compared to those calculated from a conventional NS-based finite difference (FD) simulation. In the present study, special care was taken to make sure the computational domains for LBM and FD simulations were the same. Similar validation studies in the literature have used LBM simulations with smaller computational domains in order to reduce the computational cost. However, reducing the size of the computational domain affects the turbulence statistics and confounds the results of the validation. The turbulence statistics calculated from the LBM and FD simulations were found to agree qualitatively; however, there were several significant deviations, particularly in the variance profiles. The largest discrepancy was in the variance of the pressure fluctuations, which differed by approximately 7%. Given that both the LBM and FD simulations resolved the full range of turbulent scales and no models were used, this error was deemed to be significant. The cause of the discrepancy in the pressure variance was found to be the compressibility of the LBM. The LBM allows the density to vary, while the FD method does not since it solves the incompressible form of the NS equations. The effect of the compressibility could be reduced by lowering the Mach number, but this would come at the cost of significantly increasing the computational cost. Therefore, the conclusion of this work is that, while the LBM is capable of producing accurate solutions for incompressible turbulent flows, it is significantly more expensive than conventional methods for simple wall-bounded turbulent flows.

Subjects/Keywords: Lattice Boltzmann Method ; Direct Numerical Simulation ; Turbulence

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APA (6^th Edition):

Bespalko, D. J. (2011). Validation of the Lattice Boltzmann Method for Direct Numerical Simulation of Wall-Bounded Turbulent Flows . (Thesis). Queens University. Retrieved from http://hdl.handle.net/1974/6729

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Bespalko, Dustin John. “Validation of the Lattice Boltzmann Method for Direct Numerical Simulation of Wall-Bounded Turbulent Flows .” 2011. Thesis, Queens University. Accessed January 17, 2021. http://hdl.handle.net/1974/6729.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Bespalko, Dustin John. “Validation of the Lattice Boltzmann Method for Direct Numerical Simulation of Wall-Bounded Turbulent Flows .” 2011. Web. 17 Jan 2021.

Vancouver:

Bespalko DJ. Validation of the Lattice Boltzmann Method for Direct Numerical Simulation of Wall-Bounded Turbulent Flows . [Internet] [Thesis]. Queens University; 2011. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1974/6729.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Bespalko DJ. Validation of the Lattice Boltzmann Method for Direct Numerical Simulation of Wall-Bounded Turbulent Flows . [Thesis]. Queens University; 2011. Available from: http://hdl.handle.net/1974/6729

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

3. 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 (6^th 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 (16^th Edition):

Graham, Jason Scott. “Turbulence simulations: multiscale modeling and data-intensive computing methodologies.” 2014. Thesis, Johns Hopkins University. Accessed January 17, 2021. http://jhir.library.jhu.edu/handle/1774.2/37045.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Graham, Jason Scott. “Turbulence simulations: multiscale modeling and data-intensive computing methodologies.” 2014. Web. 17 Jan 2021.

Vancouver:

Graham JS. Turbulence simulations: multiscale modeling and data-intensive computing methodologies. [Internet] [Thesis]. Johns Hopkins University; 2014. [cited 2021 Jan 17]. 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

Princeton University

4. MacArt, Jonathan Francis. Computational Simulation and Modeling of Heat Release Effects on Turbulence in Turbulent Reacting Flow .

Degree: PhD, 2018, Princeton University

URL: http://arks.princeton.edu/ark:/88435/dsp015425kd39x

► This dissertation concerns the analysis and modeling of turbulence dynamics in turbulent combustion. In certain regimes of turbulent combustion, dilatation (volumetric expansion) induced by chemical… (more)

▼ This dissertation concerns the analysis and modeling of turbulence dynamics in turbulent combustion. In certain regimes of turbulent combustion, dilatation (volumetric expansion) induced by chemical heat release can result in significant modification of turbulence dynamics, leading to the failure of most common turbulence models used in predictive simulations. In this dissertation, the physical mechanisms of interaction between chemical heat release and turbulence are analyzed, scaling theories for the regime dependence of these effects are confirmed, and new turbulence models are introduced to account for these interactions. Numerical simulation forms the foundation of the analyses in this dissertation. Using a common planar jet configuration, a range of turbulent combustion regimes is accessed via Direct Numerical Simulation (DNS). In order to conduct these simulations accurately and efficiently on large-scale parallel computers, advanced numerical algorithms are introduced. These schemes improve the accuracy of state-of-the-art schemes and reduce the computational cost by approximately a factor of two. In nonpremixed combustion, heat release effects on turbulence are observed at low turbulent Reynolds number (the ratio of inertial forces to viscous forces), but the impact on turbulence model validity is minimal due to the greatly reduced turbulence intensity. In premixed combustion, scaling theories for the dependence of dilatation effects on Karlovitz number (the ratio of the flame time scale to the Kolmogorov time scale) are confirmed for the first time in turbulent shear flows. Algebraic combinations of limit-state turbulence models are proposed to account for counter-gradient transport in low Karlovitz number premixed combustion. A variable "efficiency function" controls the regime dependence of counter-gradient effects, and these models are verified a priori using the DNS databases. The algebraic approach successfully captures counter-gradient transport in the flame-normal direction, but the linear nature of these models precludes them from capturing other effects of heat release including effects of instantaneous flame motion. Finally, a new statistical description of turbulence is introduced by conditioning on an independent flame coordinate. Turbulence statistics obtained in this framework explicitly account for effects of flame motion and chemical heat release. Budgets of conditional mean velocity and turbulent kinetic energy are computed, and modeling implications are discussed. Advisors/Committee Members: Mueller, Michael E (advisor).

Subjects/Keywords: Conditional statistics; Direct Numerical Simulation; Numerical analysis; Turbulence modeling; Turbulent combustion

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APA (6^th Edition):

MacArt, J. F. (2018). Computational Simulation and Modeling of Heat Release Effects on Turbulence in Turbulent Reacting Flow . (Doctoral Dissertation). Princeton University. Retrieved from http://arks.princeton.edu/ark:/88435/dsp015425kd39x

Chicago Manual of Style (16^th Edition):

MacArt, Jonathan Francis. “Computational Simulation and Modeling of Heat Release Effects on Turbulence in Turbulent Reacting Flow .” 2018. Doctoral Dissertation, Princeton University. Accessed January 17, 2021. http://arks.princeton.edu/ark:/88435/dsp015425kd39x.

MLA Handbook (7^th Edition):

MacArt, Jonathan Francis. “Computational Simulation and Modeling of Heat Release Effects on Turbulence in Turbulent Reacting Flow .” 2018. Web. 17 Jan 2021.

Vancouver:

MacArt JF. Computational Simulation and Modeling of Heat Release Effects on Turbulence in Turbulent Reacting Flow . [Internet] [Doctoral dissertation]. Princeton University; 2018. [cited 2021 Jan 17]. Available from: http://arks.princeton.edu/ark:/88435/dsp015425kd39x.

Council of Science Editors:

MacArt JF. Computational Simulation and Modeling of Heat Release Effects on Turbulence in Turbulent Reacting Flow . [Doctoral Dissertation]. Princeton University; 2018. Available from: http://arks.princeton.edu/ark:/88435/dsp015425kd39x

5. Roblin, Simon. Etude numérique de l'auto-inflammation des solides par simulation numérique directe : application au polyméthacrylate de méthyle : Numerical Study of Solid Fuels Auto-Ignition Using Direct Numerical Simulation : Application to the Polymethyl Methacrylate.

Degree: Docteur es, Energétique, thermique, combustion, 2016, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique

URL: http://www.theses.fr/2016ESMA0023

►

La propagation des incendies à l’échelle de locaux et de villes est un enjeu majeur. Elle est notamment conditionnée par l’inflammation des matériaux dans les… (more)

▼

La propagation des incendies à l’échelle de locaux et de villes est un enjeu majeur. Elle est notamment conditionnée par l’inflammation des matériaux dans les locaux attenants au sinistre. Cette dernière résulte de l’allumage du mélange gazeux combustible issu de la décomposition thermique de la phase condensée.Deux types d’inflammation sont définis dans la littérature : l’inflammation pilotée par la présence d’une source d’allumage, et l’auto-inflammation, résultant de l’emballement de la réaction dans la phase gazeuse. L’auto-inflammation joue un rôle majeur dans le contexte d’une propagation de local à local. Toutefois, ce processus n’a été que très peu étudié expérimentalement du fait de sa complexité et seules des analyses théoriques sont aujourd’hui disponibles concernant les phénomènes en jeu.L’enjeu de la présente étude est de caractériser les régimes d’autoallumage en fonction de différentes typologies de solide (comportement thermique et cinétique), afin de mieux comprendre leurs processus et leurs conditions d’occurrence. Cette compréhension fine permet alors de développer des modèles plus globaux de propagation pour une considération déterministe du risque incendie à l’échelle urbaine.Le caractère bref et local de l’auto-inflammation impose le choix d’une méthode de résolution complète des écoulements, des transferts et de la chimie. La Simulation Numérique Directe (DNS) a donc été sélectionnée afin de capter ces phénomènes, avec l’introduction d’une cinétique fine et non infiniment rapide de la décomposition thermique et de la combustion.

Fire propagation on the scale of buildings and cities is a major stake. It is conditioned by the ignition of solid fuels in rooms adjacent to the one where the disaster originally takes place. The ignition is so piloted by the initiation of the combustion reaction of the gaseous mixture stemming from the thermal decomposition of the condensed phase induced by heat transfer.Two types of ignition are defined in the literature: piloted-ignition related to the presence of a hot spot and auto-ignition resulting from the thermal runaway within the gas phase. The auto-ignition plays a major role in the context of fire spread between rooms. However, this process has been very little experimentally studied, because of its complexity, and only theoretical analyses were lead concerning the phenomena which take place during solid fuels auto ignition.The aim of the present study is to characterize auto-ignition regimes according to various solid typologies (regarding to thermal and kinetic behaviour) in order to understand better their processes and their occurrence conditions. Thereby, this fine understanding allows to develop global models of fire spread for a deterministic consideration of the fire hazards at urban scale.The brief and local character of the auto-ignition requires the choice of a complete resolution for flows, transfers and chemistry. Thus, the Direct Numerical Simulation (DNS) was selected to capture the phenomena, with the introduction of a fine and…

Advisors/Committee Members: Rogaume, Thomas (thesis director), Richard, Franck (thesis director).

Subjects/Keywords: Densité volumique de masse; Simulation numérique directe; Density; Direct numerical simulation

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APA (6^th Edition):

Roblin, S. (2016). Etude numérique de l'auto-inflammation des solides par simulation numérique directe : application au polyméthacrylate de méthyle : Numerical Study of Solid Fuels Auto-Ignition Using Direct Numerical Simulation : Application to the Polymethyl Methacrylate. (Doctoral Dissertation). Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Retrieved from http://www.theses.fr/2016ESMA0023

Chicago Manual of Style (16^th Edition):

Roblin, Simon. “Etude numérique de l'auto-inflammation des solides par simulation numérique directe : application au polyméthacrylate de méthyle : Numerical Study of Solid Fuels Auto-Ignition Using Direct Numerical Simulation : Application to the Polymethyl Methacrylate.” 2016. Doctoral Dissertation, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Accessed January 17, 2021. http://www.theses.fr/2016ESMA0023.

MLA Handbook (7^th Edition):

Roblin, Simon. “Etude numérique de l'auto-inflammation des solides par simulation numérique directe : application au polyméthacrylate de méthyle : Numerical Study of Solid Fuels Auto-Ignition Using Direct Numerical Simulation : Application to the Polymethyl Methacrylate.” 2016. Web. 17 Jan 2021.

Vancouver:

Roblin S. Etude numérique de l'auto-inflammation des solides par simulation numérique directe : application au polyméthacrylate de méthyle : Numerical Study of Solid Fuels Auto-Ignition Using Direct Numerical Simulation : Application to the Polymethyl Methacrylate. [Internet] [Doctoral dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2016. [cited 2021 Jan 17]. Available from: http://www.theses.fr/2016ESMA0023.

Council of Science Editors:

Roblin S. Etude numérique de l'auto-inflammation des solides par simulation numérique directe : application au polyméthacrylate de méthyle : Numerical Study of Solid Fuels Auto-Ignition Using Direct Numerical Simulation : Application to the Polymethyl Methacrylate. [Doctoral Dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2016. Available from: http://www.theses.fr/2016ESMA0023

UCLA

6. Park, Hyunwook. A Numerical Study of the Effects of Superhydrophobic Surfaces on Skin-Friction Drag Reduction in Wall-Bounded Shear Flows.

Degree: Mechanical Engineering, 2015, UCLA

URL: http://www.escholarship.org/uc/item/4vz7m8hb

► Recent developments of superhydrophobic surfaces (SHSs) have attracted much attention because of the possibility of achieving substantial skin-friction drag reduction at high Reynolds number turbulent… (more)

▼ Recent developments of superhydrophobic surfaces (SHSs) have attracted much attention because of the possibility of achieving substantial skin-friction drag reduction at high Reynolds number turbulent flows. An SHS, consisting of a hydrophobic surface combined with micro- or nano-scaled topological features, can yield an effective slip length on the order of several hundred microns. In this numerical study, direct numerical simulations of turbulent channel flows and turbulent boundary layers (TBLs) developing over SHSs were performed. An SHS was modeled through the shear-free boundary condition, assuming the sustainable gas-liquid interface remained as a flat surface. For the considered Reynolds number ranges and SHS geometries, it was found that the effective slip length normalized by viscous wall units was the key parameter and the effective slip length should be on the order of the buffer layer in order to have the maximum benefit of drag reduction. The effective surface slip length can be interpreted as a depth of influence into which SHSs affect the flow in the wall-normal direction. This result demonstrates that an SHS achieves its drag reduction by affecting the turbulence structures within the buffer layer of wall-bounded turbulent flow. It was also found that the width of an SHS, relative to the spanwise width of near-wall turbulence structures, was also a key parameter to the total amount of drag reduction. Significant suppression of near-wall turbulence structures were observed, which resulted in large skin-friction drag reduction due to the lack of the shear over SHSs. A comparison between TBLs and turbulent channel flows over SHSs were also examined. In contrast to fully developed turbulent channel flows, the effective slip velocity and hence the effective slip length varied in the streamwise direction of TBL, implying that total drag reduction of TBL would depend on the streamwise length of a given SHS. The present numerical study was compared with recent experimental results and showed good agreement. In addition to flow and SHS geometry conditions, the streamwise length of SHSs was also a key factor to understand the underlying physics of wall-bounded shear flows. Finally, it was found that the amount of drag reduction was theoretically estimated as a function of the effective slip length normalized by viscous wall units.

Subjects/Keywords: Mechanical engineering; Direct Numerical Simulation; Drag Reduction; Superhydrophobic Surfaces

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Park, H. (2015). A Numerical Study of the Effects of Superhydrophobic Surfaces on Skin-Friction Drag Reduction in Wall-Bounded Shear Flows. (Thesis). UCLA. Retrieved from http://www.escholarship.org/uc/item/4vz7m8hb

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Park, Hyunwook. “A Numerical Study of the Effects of Superhydrophobic Surfaces on Skin-Friction Drag Reduction in Wall-Bounded Shear Flows.” 2015. Thesis, UCLA. Accessed January 17, 2021. http://www.escholarship.org/uc/item/4vz7m8hb.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Park, Hyunwook. “A Numerical Study of the Effects of Superhydrophobic Surfaces on Skin-Friction Drag Reduction in Wall-Bounded Shear Flows.” 2015. Web. 17 Jan 2021.

Vancouver:

Park H. A Numerical Study of the Effects of Superhydrophobic Surfaces on Skin-Friction Drag Reduction in Wall-Bounded Shear Flows. [Internet] [Thesis]. UCLA; 2015. [cited 2021 Jan 17]. Available from: http://www.escholarship.org/uc/item/4vz7m8hb.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Park H. A Numerical Study of the Effects of Superhydrophobic Surfaces on Skin-Friction Drag Reduction in Wall-Bounded Shear Flows. [Thesis]. UCLA; 2015. Available from: http://www.escholarship.org/uc/item/4vz7m8hb

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Waterloo

7. Christopher, Nicholas. Numerical Analysis of Transpiration Cooling on a Turbulent Flat Plate.

Degree: 2020, University of Waterloo

URL: http://hdl.handle.net/10012/15463

► Transpiration cooling is a promising thermal protection system for gas turbines, atmospheric re-entry heat shields, and rocket engine combustion chambers. Design of transpiration cooling systems… (more)

▼ Transpiration cooling is a promising thermal protection system for gas turbines, atmospheric re-entry heat shields, and rocket engine combustion chambers. Design of transpiration cooling systems must rely on numerical simulation in order to reduce costs. The purpose of this work it to better understand the physical phenomena which effect turbulence and heat transfer in a turbulent boundary layer with transpiration cooling, in order to inform models of the system. Towards this goal, direct numerical simulations (DNS) of transpiration cooling in a turbulent flat-plate boundary layer at a freestream mach number of 0.3 have been performed. The coolant and the hot gas are both air, and isothermal walls and coolant at a temperature ratio of Tw/T∞ = 0.5 have been prescribed. The blowing ratio (which is the mass flux ratio between the coolant and the freestream gas), and the coolant injection boundary conditions have been varied to investigate their effects on the flow. It is found that by increasing the blowing ratio, the peak turbulent kinetic energy moves away from the wall to a region of shear between the low-momentum coolant and high-momentum hot gas. As the blowing ratio is increased, there is also a reduction in heat transfer to the porous wall. This reduction of wall heat transfer is caused by the combined effects of heat advection due to the non-zero wall-normal velocity at the wall, and the reduction of the average boundary-layer temperature due to the accumulation of coolant. A new model for the latter effect is proposed which is physically realistic in the limit cases. The proposed combined model accounts for both heat advection and film accumulation and shows good agreement with the DNS data. An increase in turbulent transport of heat with increasing blowing rate is caused by the production of vortices between the coolant and hot gas. This causes a reduction in the cooling effectiveness, and can be seen near the leading edge of the transpiration region. Log law scaling of the velocity profile with blowing walls is analyzed, and found to only be applicable for modest blowing rates. Reasons for the failure of scaling laws at high blowing rates are proposed based on the x-momentum balance of the Navier-Stokes equations. In order to investigate wall modelling effects, simulations with uniform coolant injection have been compared to simulations with injection via many small slits. It is observed that as the slits get smaller (at fixed total mass flow rate and fixed wall porosity), the results trend towards the uniform injection case. Therefore, it is hypothesized that for small pore sizes, neglecting the effects of the individual pores in the wall boundary condition is physically justifiable.

Subjects/Keywords: rocket; thermal protection system; transpiration cooling; direct numerical simulation

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APA (6^th Edition):

Christopher, N. (2020). Numerical Analysis of Transpiration Cooling on a Turbulent Flat Plate. (Thesis). University of Waterloo. Retrieved from http://hdl.handle.net/10012/15463

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Christopher, Nicholas. “Numerical Analysis of Transpiration Cooling on a Turbulent Flat Plate.” 2020. Thesis, University of Waterloo. Accessed January 17, 2021. http://hdl.handle.net/10012/15463.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Christopher, Nicholas. “Numerical Analysis of Transpiration Cooling on a Turbulent Flat Plate.” 2020. Web. 17 Jan 2021.

Vancouver:

Christopher N. Numerical Analysis of Transpiration Cooling on a Turbulent Flat Plate. [Internet] [Thesis]. University of Waterloo; 2020. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10012/15463.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Christopher N. Numerical Analysis of Transpiration Cooling on a Turbulent Flat Plate. [Thesis]. University of Waterloo; 2020. Available from: http://hdl.handle.net/10012/15463

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Brigham Young University

8. Gibson, Jeffrey Reed. Direct Numerical Simulation of Transonic Wake Flow in the Presence of an Adverse Pressure Gradient and Streamline Curvature.

Degree: MS, 2011, Brigham Young University

URL: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3794&context=etd

► Wakes are present in many engineering flows. These flows include internal flows such as mixing chambers and turbomachinery as well as external flows like… (more)

▼ Wakes are present in many engineering flows. These flows include internal flows such as mixing chambers and turbomachinery as well as external flows like flow over high-lift or multi-element airfoils. Many times these wakes are exposed to flow conditions such as adverse pressure gradients and streamline curvature that alter the mean flow and turbulent structure of the wake. The ability to understand how pressure gradients and streamline curvature affects the structure of the wake is essential to predicting how the wake will affect the performance of the application in which it is found. The effects of pressure gradients and curvature of low-speed wakes has been extensively documented. As the transonic flow regime is becoming of more interest as gas speeds in turbomachinery increase this work fills a void in the body of wake knowledge pertaining to curved wakes in high speed flows. An under-resolved direct numerical simulation of transonic wake flow being shed by a cambered airfoil in the presence of adverse pressure gradients and streamline curvature is therefore presented here. It was observed that the turbulence characteristics arising from the cambered airfoil that generates the wake dominate the evolution of the wake for different distances downstream depending on the component of the Reynolds stresses that is being considered. These characteristics dissipated the most quickly in the shear stresses and endured the longest in the tangential normal stresses. Previous work in low-speed wakes has indicated that curvature creates new production terms that translate into asymmetry in the profiles of the wake. Curvature was observed to have limited influence on the evolution of the streamwise normal stresses and an extensive impact on the tangential normal stresses. The transport of the Reynolds shear stresses indicate that the asymmetry in this stress is caused indeed by curvature but through turbulent diffusion and not production. The k-ε turbulence model overpredicted the effect of curvature on the turbulence stresses in the wake. This led to accelerated wake decay and spread compared to the UDNS data.

Subjects/Keywords: direct numerical simulation; curvature; wakes; cfd; pressure gradients; Mechanical Engineering

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APA (6^th Edition):

Gibson, J. R. (2011). Direct Numerical Simulation of Transonic Wake Flow in the Presence of an Adverse Pressure Gradient and Streamline Curvature. (Masters Thesis). Brigham Young University. Retrieved from https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3794&context=etd

Chicago Manual of Style (16^th Edition):

Gibson, Jeffrey Reed. “Direct Numerical Simulation of Transonic Wake Flow in the Presence of an Adverse Pressure Gradient and Streamline Curvature.” 2011. Masters Thesis, Brigham Young University. Accessed January 17, 2021. https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3794&context=etd.

MLA Handbook (7^th Edition):

Gibson, Jeffrey Reed. “Direct Numerical Simulation of Transonic Wake Flow in the Presence of an Adverse Pressure Gradient and Streamline Curvature.” 2011. Web. 17 Jan 2021.

Vancouver:

Gibson JR. Direct Numerical Simulation of Transonic Wake Flow in the Presence of an Adverse Pressure Gradient and Streamline Curvature. [Internet] [Masters thesis]. Brigham Young University; 2011. [cited 2021 Jan 17]. Available from: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3794&context=etd.

Council of Science Editors:

Gibson JR. Direct Numerical Simulation of Transonic Wake Flow in the Presence of an Adverse Pressure Gradient and Streamline Curvature. [Masters Thesis]. Brigham Young University; 2011. Available from: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3794&context=etd

9. Nivarti, Girish Venkata. The bending effect in turbulent flame propagation.

Degree: PhD, 2017, University of Cambridge

URL: https://www.repository.cam.ac.uk/handle/1810/270335

► In the present thesis, the sensitivity of flame propagation to the turbulent motion of burning gases is investigated. The long-standing issue of the 'bending effect'… (more)

▼ In the present thesis, the sensitivity of flame propagation to the turbulent motion of burning gases is investigated. The long-standing issue of the 'bending effect' is focused upon, which refers to the experimentally-observed inhibition of flame propagation velocity at high intensities of turbulence. Plausible mechanisms for the bending effect are investigated by isolating systematically the effects of turbulence intensity. By providing a novel perspective on this topic, the thesis addresses the fundamental limits of turbulent burning. The investigation employs Direct Numerical Simulation (DNS), which enables the basic conditions of burning to be controlled directly. A parametric DNS dataset is designed and generated by increasing turbulence intensity over five separate simulations. Effects of turbulent motion are isolated in this manner, such that the bending effect is reproduced in the variation of flame propagation velocity recorded. Subsequently, the validity of Damköhler's hypotheses is investigated to ascertain the mechanism of bending. Analysis of the DNS dataset highlights the significance of kinematic flame response in determining turbulent flame propagation. Damköhler's first hypothesis is found to be valid throughout the dataset, suggesting that the bending effect may be a consequence of self-regulation of the flame surface. This contradicts the dominant belief that bending occurs as a result of flame surface disruption by the action of turbulence. Damköhler's second hypothesis is found to be valid in a relatively limited regime within the dataset, its validity governed by flame-induced effects on the prescribed turbulent flow field. Therefore, this thesis presents turbulent flame propagation and the bending effect as emergent from the dynamics of a flame surface that retains its internal thermo-chemical structure. Finally, experimental validation is sought for the proposed mechanisms of bending. Comparisons have been initiated with measurements in the Leeds explosion vessel, based on which the widely accepted mechanism of bending was hypothesized twenty-five years ago. Modifications to the DNS framework warranted by this comparison have aided the development of novel computationally-efficient algorithms. The ongoing work may yield insights into the key mechanism of the bending effect in turbulent flame propagation.

Subjects/Keywords: Turbulence; Flame propagation; Bending effect; Direct Numerical Simulation; Premixed Flames

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APA (6^th Edition):

Nivarti, G. V. (2017). The bending effect in turbulent flame propagation. (Doctoral Dissertation). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/270335

Chicago Manual of Style (16^th Edition):

Nivarti, Girish Venkata. “The bending effect in turbulent flame propagation.” 2017. Doctoral Dissertation, University of Cambridge. Accessed January 17, 2021. https://www.repository.cam.ac.uk/handle/1810/270335.

MLA Handbook (7^th Edition):

Nivarti, Girish Venkata. “The bending effect in turbulent flame propagation.” 2017. Web. 17 Jan 2021.

Vancouver:

Nivarti GV. The bending effect in turbulent flame propagation. [Internet] [Doctoral dissertation]. University of Cambridge; 2017. [cited 2021 Jan 17]. Available from: https://www.repository.cam.ac.uk/handle/1810/270335.

Council of Science Editors:

Nivarti GV. The bending effect in turbulent flame propagation. [Doctoral Dissertation]. University of Cambridge; 2017. Available from: https://www.repository.cam.ac.uk/handle/1810/270335

University of Manitoba

10. Yan, Jiaxin. Direct numerical simulation of turbulent flows in a rectangular duct of different aspect ratios.

Degree: Mechanical Engineering, 2018, University of Manitoba

URL: http://hdl.handle.net/1993/33297

► Direct numerical simulations are performed to investigate turbulent flows in a rectangular duct of aspect ratio varying from 1.0 to 3.0 at a fixed low… (more)

Subjects/Keywords: Direct numerical simulation; Turbulent flow; Rectangular duct; Coherent structures

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APA (6^th Edition):

Yan, J. (2018). Direct numerical simulation of turbulent flows in a rectangular duct of different aspect ratios. (Masters Thesis). University of Manitoba. Retrieved from http://hdl.handle.net/1993/33297

Chicago Manual of Style (16^th Edition):

Yan, Jiaxin. “Direct numerical simulation of turbulent flows in a rectangular duct of different aspect ratios.” 2018. Masters Thesis, University of Manitoba. Accessed January 17, 2021. http://hdl.handle.net/1993/33297.

MLA Handbook (7^th Edition):

Yan, Jiaxin. “Direct numerical simulation of turbulent flows in a rectangular duct of different aspect ratios.” 2018. Web. 17 Jan 2021.

Vancouver:

Yan J. Direct numerical simulation of turbulent flows in a rectangular duct of different aspect ratios. [Internet] [Masters thesis]. University of Manitoba; 2018. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1993/33297.

Council of Science Editors:

Yan J. Direct numerical simulation of turbulent flows in a rectangular duct of different aspect ratios. [Masters Thesis]. University of Manitoba; 2018. Available from: http://hdl.handle.net/1993/33297

University of Manitoba

11. Lozowy, Richard. Hemodynamics in abdominal aorta aneurysms.

Degree: Mechanical Engineering, 2017, University of Manitoba

URL: http://hdl.handle.net/1993/32873

► This thesis presents results from numerical simulations of pulsatile fluid flow in canonical channel geometry and patient-specific abdominal aortic aneurysms (AAA). An AAA is a… (more)

▼ This thesis presents results from numerical simulations of pulsatile fluid flow in canonical channel geometry and patient-specific abdominal aortic aneurysms (AAA). An AAA is a dilatation of the aortic segment between the renal arteries and the iliac bifurcation. The continuing expansion of an AAA weakens the wall and potentially leads to rupture. Intraluminal thrombus (ILT) deposition is the coagulation of platelets and often accumulates along the wall in AAA. The presence of ILT may decrease the flow of oxygen to the wall and the region of the AAA with ILT could be more susceptible to further expansion or rupture. Knowledge of AAA shapes that cause adverse hemodynamics could be used to establish criteria to help determine when to operate on a particular AAA to prevent rupture. It was determined that some AAA shapes experience non-disturbed hemodynamics that do not significantly deviate from normal-sized aorta. For other AAA shapes a turbulent jet forms distal to the aneurysms neck and impinges against the AAA wall. It was found that at the location the jet impinges the wall was devoid of ILT and away from this location ILT often accumulated. It was suspected that the high wall-tangent shearing force from the impact of flow vortexes prevents attachment of cellular material to the wall. Although impingement prevents ILT, in all cases the AAA was found to be expanding in the direction the neck angled the flow vortexes and it was reasoned that the wall-normal pressure force from vortex impact causes the expansion. The triple decomposition method is used to segment blood flow into its periodic and turbulent components. Another segmentation method, dynamic mode decomposition (DMD) is used to segment blood flow into modes oscillating at specific frequencies. A low-order representation of the velocity field was then reconstructed using only the modes oscillating at the pulse frequency. This procedure removes both the higher-frequency turbulent and periodic oscillations from the velocity field. The resulting reconstruction shows a simplified representation of the blood flow dynamics in the AAA, such that it consists of a single large-scale vortex. Advisors/Committee Members: Kuhn, David (Mechanical Engineering) Boyd, April (Surgery) (supervisor), Wang, BingChen (Mechanical Engineering) Morrison, Jason (Biosystems Engineering) Steinman, David (Mechanical and Industrial Engineering, University of Toronto) (examiningcommittee).

Subjects/Keywords: Abdominal aorta aneurysm; Dynamic mode decomposition; Direct numerical simulation; Turbulence

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APA (6^th Edition):

Lozowy, R. (2017). Hemodynamics in abdominal aorta aneurysms. (Thesis). University of Manitoba. Retrieved from http://hdl.handle.net/1993/32873

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Lozowy, Richard. “Hemodynamics in abdominal aorta aneurysms.” 2017. Thesis, University of Manitoba. Accessed January 17, 2021. http://hdl.handle.net/1993/32873.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Lozowy, Richard. “Hemodynamics in abdominal aorta aneurysms.” 2017. Web. 17 Jan 2021.

Vancouver:

Lozowy R. Hemodynamics in abdominal aorta aneurysms. [Internet] [Thesis]. University of Manitoba; 2017. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1993/32873.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Lozowy R. Hemodynamics in abdominal aorta aneurysms. [Thesis]. University of Manitoba; 2017. Available from: http://hdl.handle.net/1993/32873

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Manitoba

12. Nasseri Oskouie, Shahin. Dispersion and mixing of plumes in wall-bounded and isotropic turbulent flows.

Degree: Mechanical Engineering, 2016, University of Manitoba

URL: http://hdl.handle.net/1993/31606

► The dispersion and mixing of passive scalars released from two concentrated sources into open-channel and homogeneous isotropic turbulent flows are studied using direct numerical simulation… (more)

▼ The dispersion and mixing of passive scalars released from two concentrated sources into open-channel and homogeneous isotropic turbulent flows are studied using direct numerical simulation (DNS). The simulations are conducted using two fully-parallelized in-house codes developed using the FORTRAN 90/95 programming language. A comparative study has been conducted to investigate the effects of the source separation distance, Reynolds number, relative length scales of the plume and turbulent flow, and source elevation on the dispersion and mixing of two plumes. For both flow configurations, four distinct stages in the downwind development of the cross correlation between the fluctuating concentration fields have been identified which feature zero, destructive and constructive interferences and a complete mixing state. Differences between the exceedance probability of concentrations for the single and total plumes are highlighted and analyzed, and the effects of destructive and constructive interference on the exceedance probabilities for the total plume are used to explain these differences. It is found that the relationship between the third- and fourth-order concentration moments and the second-order concentration moment can be well predicted using a clipped-gamma model. This leads to an interesting conclusion that all the higher-order (third-order and above) moments of the total concentration can be inferred from a knowledge of only the first- and second-order concentration moments of each single plume and of the cross correlation coefficient. From a spectral analysis, it is observed that there exists a range of `leading scales' at which the rate of turbulent mixing of the two plumes becomes the most efficient and the coherency spectrum of the plumes approaches the asymptotic value of unity quicker than at any other scales. Advisors/Committee Members: Wang, Bing-Chen (Mechanical Engineering) Yee, Eugene (Defence R&D Canada) (supervisor), Kuhn, David (Mechanical Engineering) Okhmatovski, Vladimir (Electrical Engineering).

Subjects/Keywords: Plume interference; Dispersion; Passive scalar; Direct Numerical Simulation (DNS); Turbulence

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APA (6^th Edition):

Nasseri Oskouie, S. (2016). Dispersion and mixing of plumes in wall-bounded and isotropic turbulent flows. (Thesis). University of Manitoba. Retrieved from http://hdl.handle.net/1993/31606

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Nasseri Oskouie, Shahin. “Dispersion and mixing of plumes in wall-bounded and isotropic turbulent flows.” 2016. Thesis, University of Manitoba. Accessed January 17, 2021. http://hdl.handle.net/1993/31606.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Nasseri Oskouie, Shahin. “Dispersion and mixing of plumes in wall-bounded and isotropic turbulent flows.” 2016. Web. 17 Jan 2021.

Vancouver:

Nasseri Oskouie S. Dispersion and mixing of plumes in wall-bounded and isotropic turbulent flows. [Internet] [Thesis]. University of Manitoba; 2016. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1993/31606.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Nasseri Oskouie S. Dispersion and mixing of plumes in wall-bounded and isotropic turbulent flows. [Thesis]. University of Manitoba; 2016. Available from: http://hdl.handle.net/1993/31606

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Aberdeen

13. Seddighi-Moormani, Mehdi. Study of turbulence and wall shear stress in unsteady flow over smooth and rough wall surfaces.

Degree: PhD, 2011, University of Aberdeen

URL: https://eu03.alma.exlibrisgroup.com/view/delivery/44ABE_INST/12153288260005941 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540452

► Flows over hydraulically smooth walls are predominant in turbulence studies whereas real surfaces in engineering applications are often rough. This is important because turbulent flows… (more)

▼ Flows over hydraulically smooth walls are predominant in turbulence studies whereas real surfaces in engineering applications are often rough. This is important because turbulent flows close to the two types of surface can exhibit large differences. Unfortunately, neither experimental studies nor theoretical studies based on conventional computational fluid dynamics (CFD) can give sufficiently accurate, detailed information about unsteady turbulent flow behaviour close to solid surfaces, even for smooth wall cases. In this thesis, therefore, use is made of a state of the art computational method “Direct Numerical Simulation (DNS)” to investigate the unsteady flows. An “in-house” DNS computer code is developed for the study reported in this thesis. Spatial discretization in the code is achieved using a second order, finite difference method. The semi-implicit (Runge-Kutta & Crank-Nicholson) time advancement is incorporated into the fractional-step method. A Fast Fourier Transform solver is used for solving the Poisson equation. An efficient immersed Boundary Method (IBM) is used for treating the roughness. The code is parallelized using a Message Passing Interface (MPI) and it is adopted for use on a distributed-memory computer cluster at University of Aberdeen as well as for use at the UK’s national high-performance computing service, HECToR. As one of the first DNS of accelerating/decelerating flows over smooth and rough walls, the study has produced detailed new information on turbulence behaviours which can be used for turbulence model development and validations. The detailed data have enabled better understanding of the flow physics to be developed. The results revealed strong non-equilibrium and anisotropic behaviours of turbulence dynamics in such flows. The preliminary results on the rough wall flow show the response of turbulence in the core and wall regions, and the relationship between the axial and the other components are significantly different from those in smooth wall flows.

Subjects/Keywords: 502.85; Turbulence; Surface roughness; Fluid dynamics; Direct numerical simulation

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APA (6^th Edition):

Seddighi-Moormani, M. (2011). Study of turbulence and wall shear stress in unsteady flow over smooth and rough wall surfaces. (Doctoral Dissertation). University of Aberdeen. Retrieved from https://eu03.alma.exlibrisgroup.com/view/delivery/44ABE_INST/12153288260005941 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540452

Chicago Manual of Style (16^th Edition):

Seddighi-Moormani, Mehdi. “Study of turbulence and wall shear stress in unsteady flow over smooth and rough wall surfaces.” 2011. Doctoral Dissertation, University of Aberdeen. Accessed January 17, 2021. https://eu03.alma.exlibrisgroup.com/view/delivery/44ABE_INST/12153288260005941 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540452.

MLA Handbook (7^th Edition):

Seddighi-Moormani, Mehdi. “Study of turbulence and wall shear stress in unsteady flow over smooth and rough wall surfaces.” 2011. Web. 17 Jan 2021.

Vancouver:

Seddighi-Moormani M. Study of turbulence and wall shear stress in unsteady flow over smooth and rough wall surfaces. [Internet] [Doctoral dissertation]. University of Aberdeen; 2011. [cited 2021 Jan 17]. Available from: https://eu03.alma.exlibrisgroup.com/view/delivery/44ABE_INST/12153288260005941 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540452.

Council of Science Editors:

Seddighi-Moormani M. Study of turbulence and wall shear stress in unsteady flow over smooth and rough wall surfaces. [Doctoral Dissertation]. University of Aberdeen; 2011. Available from: https://eu03.alma.exlibrisgroup.com/view/delivery/44ABE_INST/12153288260005941 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540452

Colorado School of Mines

14. Li, Xiaoqi. Simulation of proppant transport in slickwater with DNS-derived drag correlations.

Degree: PhD, Petroleum Engineering, 2018, Colorado School of Mines

URL: http://hdl.handle.net/11124/172827

► This dissertation is developed to address a need of multiphase flow models for proppant transport: problem-relevant drag correlations. This dissertation consists of small-scale simulations by… (more)

▼ This dissertation is developed to address a need of multiphase flow models for proppant transport: problem-relevant drag correlations. This dissertation consists of small-scale simulations by direct numerical simulations (DNS) and larger, fracture-scale simulations by MFIX (Multiphase Flow with Interaction eXchange). DNS was employed to study the influences of several dimensionless numbers, namely the Reynolds number of cross flow, 〖Re〗_x, the Archimedes number, Ar, consisting of gravity, density difference, slickwater viscosity, and proppant size, the density of proppants relative to that of the fracturing fluid, ρ_p⁄ρ_f , the ratio of fracture width over proppant dimension, W⁄d_p , and proppant concentration, ϕ_s. Another independent parameter was firstly evaluated in this study is the inclination angle of fracture, θ. DNS results show that W⁄d_p plays a significant role in proppant transport. Narrower fractures impede proppant settling more. Cross flow and proppant density over that of fluid (provided that Ar is held as a constant) were found to have negligible effects on the settling velocity. Ar, ϕ_s, and inclination were found to have significant influences on settling. When factures were placed with a large fracture width, the effect of proppant concentration on settling was found to be reversed from that in vertical fractures. The lower the proppant concentration, the slower proppants settle. The aim of DNS was not only to understand the influence of the dimensionless numbers, but also to obtain data for developing drag correlations. Drag correlations were developed from DNS data using quadratic polynomials and interpolations. These drag correlations were incorporated into MFIX to close the momentum equations of fluid and solid phases. MFIX simulation results include the rate of proppant bank formation and the equilibrium height and transition length of the end proppant distribution. First, DNS-derived drag correlation predicted slower proppant bank formation compared to other default drag laws, because proppant settling speed is slower in narrow fractures, a factor that to date has not been considered in proppant transport simulations. Second, the influences of key parameters, proppant size, proppant density, proppant concentration, fluid viscosity, and inclination, on proppant bank formation and distribution, were found to be mostly consistent with their roles in affecting the settling velocity. Higher settling velocity always leads to more rapid formation of proppant banks and shorter transition length. Equilibrium height of proppant bank generally increases with increasing proppant concentration and decreases with increasing fluid viscosity. Advisors/Committee Members: Yin, Xiaolong (advisor), Tilton, Nils (committee member), Miskimins, Jennifer L. (committee member), Zerpa, Luis E. (committee member), Gutierrez, Marte S. (committee member), Smits, Kathleen M. (committee member).

Subjects/Keywords: drag correlation; proppant transport; direct numerical simulation; sedimentation; Lattice Boltzmann

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APA (6^th Edition):

Li, X. (2018). Simulation of proppant transport in slickwater with DNS-derived drag correlations. (Doctoral Dissertation). Colorado School of Mines. Retrieved from http://hdl.handle.net/11124/172827

Chicago Manual of Style (16^th Edition):

Li, Xiaoqi. “Simulation of proppant transport in slickwater with DNS-derived drag correlations.” 2018. Doctoral Dissertation, Colorado School of Mines. Accessed January 17, 2021. http://hdl.handle.net/11124/172827.

MLA Handbook (7^th Edition):

Li, Xiaoqi. “Simulation of proppant transport in slickwater with DNS-derived drag correlations.” 2018. Web. 17 Jan 2021.

Vancouver:

Li X. Simulation of proppant transport in slickwater with DNS-derived drag correlations. [Internet] [Doctoral dissertation]. Colorado School of Mines; 2018. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11124/172827.

Council of Science Editors:

Li X. Simulation of proppant transport in slickwater with DNS-derived drag correlations. [Doctoral Dissertation]. Colorado School of Mines; 2018. Available from: http://hdl.handle.net/11124/172827

University of Melbourne

15. Haghiri, Ali. Sound generation by turbulent premixed flames.

Degree: 2017, University of Melbourne

URL: http://hdl.handle.net/11343/191771

► In addition to being a significant form of noise pollution, combustion noise plays a key role in the instability of many combustion systems. The noise… (more)

▼ In addition to being a significant form of noise pollution, combustion noise plays a key role in the instability of many combustion systems. The noise generated by turbulent premixed flames deserves special attention since they are common in contemporary, low-emission gas turbines. Hence, a detailed understanding of the mechanism of sound generation by premixed flames is needed for designing quieter and safer combustion systems. This thesis presents a study of sound generation by turbulent, premixed flames using both direct numerical simulation (DNS) and theory. DNS of two round jet methane/air flames with equivalence ratios of 0.7 and 1.0 are carried out. Single step chemistry is employed to reduce the computational cost, and care is taken to resolve both the near and far fields and to avoid noise reflections at the outflow boundaries. Several significant features of these two flames are noted. These include the monopolar nature of the sound from both flames, the stoichiometric flame being significantly louder than the lean flame, and the observed frequency of peak acoustic spectral amplitude being consistent with prior experimental studies. Further, the importance of different types of so-called ''flame annihilation'' events as monopolar acoustic sources is demonstrated. A simple model describing the contribution of annihilation events to the far-field sound is then proposed. This model considers the far-field sound generated by a turbulent premixed flame as the superposition of the sound radiated by individual, spherically symmetric annihilation events that occurred throughout the flame. The results show a significant contribution by these events to the overall produced sound. A statistical analysis of the data pertaining to annihilation events is then presented. The results show that annihilation events generally feature high negative values of curvature. A strong negative correlation between the flame displacement speed and curvature is also observed. Examining different terms of the flame displacement speed during flame annihilation reveals that the reaction term has the highest contribution among the others, followed by the curvature term and lastly the normal diffusion term. The Markstein number (Ma) is also calculated for both the entire flame and annihilation events. Smaller values of Ma are obtained for the annihilation events. Finally, a new linear model for response of turbulent premixed flames to stretch during flame annihilation is proposed.

Subjects/Keywords: aeroacoustics; turbulent premixed flames; direct numerical simulation; combustion noise

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Haghiri, A. (2017). Sound generation by turbulent premixed flames. (Doctoral Dissertation). University of Melbourne. Retrieved from http://hdl.handle.net/11343/191771

Chicago Manual of Style (16^th Edition):

Haghiri, Ali. “Sound generation by turbulent premixed flames.” 2017. Doctoral Dissertation, University of Melbourne. Accessed January 17, 2021. http://hdl.handle.net/11343/191771.

MLA Handbook (7^th Edition):

Haghiri, Ali. “Sound generation by turbulent premixed flames.” 2017. Web. 17 Jan 2021.

Vancouver:

Haghiri A. Sound generation by turbulent premixed flames. [Internet] [Doctoral dissertation]. University of Melbourne; 2017. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11343/191771.

Council of Science Editors:

Haghiri A. Sound generation by turbulent premixed flames. [Doctoral Dissertation]. University of Melbourne; 2017. Available from: http://hdl.handle.net/11343/191771

University of Cambridge

16. Nivarti, Girish Venkata. The bending effect in turbulent flame propagation.

Degree: PhD, 2017, University of Cambridge

URL: https://doi.org/10.17863/CAM.17198 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744410

► In the present thesis, the sensitivity of flame propagation to the turbulent motion of burning gases is investigated. The long-standing issue of the 'bending effect'… (more)

▼ In the present thesis, the sensitivity of flame propagation to the turbulent motion of burning gases is investigated. The long-standing issue of the 'bending effect' is focused upon, which refers to the experimentally-observed inhibition of flame propagation velocity at high intensities of turbulence. Plausible mechanisms for the bending effect are investigated by isolating systematically the effects of turbulence intensity. By providing a novel perspective on this topic, the thesis addresses the fundamental limits of turbulent burning. The investigation employs Direct Numerical Simulation (DNS), which enables the basic conditions of burning to be controlled directly. A parametric DNS dataset is designed and generated by increasing turbulence intensity over five separate simulations. Effects of turbulent motion are isolated in this manner, such that the bending effect is reproduced in the variation of flame propagation velocity recorded. Subsequently, the validity of Damköhler's hypotheses is investigated to ascertain the mechanism of bending. Analysis of the DNS dataset highlights the significance of kinematic flame response in determining turbulent flame propagation. Damköhler's first hypothesis is found to be valid throughout the dataset, suggesting that the bending effect may be a consequence of self-regulation of the flame surface. This contradicts the dominant belief that bending occurs as a result of flame surface disruption by the action of turbulence. Damköhler's second hypothesis is found to be valid in a relatively limited regime within the dataset, its validity governed by flame-induced effects on the prescribed turbulent flow field. Therefore, this thesis presents turbulent flame propagation and the bending effect as emergent from the dynamics of a flame surface that retains its internal thermo-chemical structure. Finally, experimental validation is sought for the proposed mechanisms of bending. Comparisons have been initiated with measurements in the Leeds explosion vessel, based on which the widely accepted mechanism of bending was hypothesized twenty-five years ago. Modifications to the DNS framework warranted by this comparison have aided the development of novel computationally-efficient algorithms. The ongoing work may yield insights into the key mechanism of the bending effect in turbulent flame propagation.

Subjects/Keywords: 662.6; Turbulence; Flame propagation; Bending effect; Direct Numerical Simulation; Premixed Flames

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Nivarti, G. V. (2017). The bending effect in turbulent flame propagation. (Doctoral Dissertation). University of Cambridge. Retrieved from https://doi.org/10.17863/CAM.17198 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744410

Chicago Manual of Style (16^th Edition):

Nivarti, Girish Venkata. “The bending effect in turbulent flame propagation.” 2017. Doctoral Dissertation, University of Cambridge. Accessed January 17, 2021. https://doi.org/10.17863/CAM.17198 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744410.

MLA Handbook (7^th Edition):

Nivarti, Girish Venkata. “The bending effect in turbulent flame propagation.” 2017. Web. 17 Jan 2021.

Vancouver:

Nivarti GV. The bending effect in turbulent flame propagation. [Internet] [Doctoral dissertation]. University of Cambridge; 2017. [cited 2021 Jan 17]. Available from: https://doi.org/10.17863/CAM.17198 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744410.

Council of Science Editors:

Nivarti GV. The bending effect in turbulent flame propagation. [Doctoral Dissertation]. University of Cambridge; 2017. Available from: https://doi.org/10.17863/CAM.17198 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744410

University of Texas – Austin

17. Singh, Ravi Ishwar. Direct numerical simulation and reaction path analysis of titania formation in flame synthesis.

Degree: MSin Engineering, Mechanical Engineering, 2012, University of Texas – Austin

URL: http://hdl.handle.net/2152/23016

► Flame-based synthesis is an attractive industrial process for the large scale generation of nanoparticles. In this aerosol process, a gasifi ed precursor is injected into… (more)

▼ Flame-based synthesis is an attractive industrial process for the large scale generation of nanoparticles. In this aerosol process, a gasifi ed precursor is injected into a high-temperature turbulent flame, where oxidation followed by particle nucleation and other solid phase dynamics create nanoparticles. Precursor oxidation, which ultimately leads to nucleation, is strongly influenced by the turbulent flame dynamics. Here, direct numerical simulation (DNS) of a canonical homogeneous flow is used to understand the interaction between a methane/air flame and titanium tetrachloride oxidation to titania. Detailed chemical kinetics is used to describe the combustion and precursor oxidation processes. Results show that the initial precursor decomposition is heavily influenced by the gas phase temperature field. However, temperature insensitivity of subsequent reactions in the precursor oxidation pathway slow down conversion to the titania. Consequently, titania formation occurs at much longer time scales compared to that of hydrocarbon oxidation. Further, only a fraction of the precursor is converted to titania, and a signi cant amount of partially-oxidized precursor species are formed. Introducing the precursor in the oxidizer stream as opposed to the fuel stream has only a minimal impact on the oxidation dynamics. In order to understand modeling issues, the DNS results are compared with the laminar flamelet model. It is shown that the flamelet assumption qualitatively reproduces the oxidation structure. Further, reduced oxygen concentration in the near-flame location critically a ffects titania formation. The DNS results also show that titania forms on the lean and rich sides of the flame. A reaction path analysis (RPA) is conducted. The results illustrate the di ffering reaction pathways of the detailed chemical mechanism depending on the composition of the mixture. The RPA results corroborate with the DNS results that titania formation is maximized at two mixture fraction values, one on the lean side of the flame, and one on the rich side. Advisors/Committee Members: Ezekoye, Ofodike A. (advisor), Raman, Venkat (advisor).

Subjects/Keywords: Direct numerical simulation (DNS); Combustion; Turbulence; Titania; Nanoparticles; Detailed chemical kinetics

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APA (6^th Edition):

Singh, R. I. (2012). Direct numerical simulation and reaction path analysis of titania formation in flame synthesis. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/23016

Chicago Manual of Style (16^th Edition):

Singh, Ravi Ishwar. “Direct numerical simulation and reaction path analysis of titania formation in flame synthesis.” 2012. Masters Thesis, University of Texas – Austin. Accessed January 17, 2021. http://hdl.handle.net/2152/23016.

MLA Handbook (7^th Edition):

Singh, Ravi Ishwar. “Direct numerical simulation and reaction path analysis of titania formation in flame synthesis.” 2012. Web. 17 Jan 2021.

Vancouver:

Singh RI. Direct numerical simulation and reaction path analysis of titania formation in flame synthesis. [Internet] [Masters thesis]. University of Texas – Austin; 2012. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2152/23016.

Council of Science Editors:

Singh RI. Direct numerical simulation and reaction path analysis of titania formation in flame synthesis. [Masters Thesis]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/23016

Oklahoma State University

18. Khan, Saadbin. Near Wall Structure and Deviation from Equilibrium in Wavy Channel Turbulence.

Degree: Mechanical and Aerospace Engineering, 2019, Oklahoma State University

URL: http://hdl.handle.net/11244/323408

► The structure of turbulent flow over non-flat surfaces is a topic of major interest in practical applications in both engineering and geophysical settings. A lot… (more)

▼ The structure of turbulent flow over non-flat surfaces is a topic of major interest in practical applications in both engineering and geophysical settings. A lot of work has been done in the fully rough regime at high Reynolds numbers where the effect on the outer layer turbulence structure and the resulting friction drag is well documented. It turns out that surface topology plays a significant role on the flow drag especially in the transitional roughness regime and therefore, is hard to characterize. Survey of literature shows that roughness function depends on the interaction of roughness height, flow Reynolds number and topology shape. In addition, if the surface topology contains large enough scales then it can impact the outer layer dynamics and in turn modulate the total frictional force. Therefore, it is important to understand the mechanisms underlying drag increase from systematically varied surface undulations in order to better interpret quantifications based on mean statistics such as roughness function. In this study, we explore the mechanisms that modulate the turbulence structure over a two-dimensional (2D) sinusoidal wavy surface with a fixed amplitude, but varying slope. To accomplish this, we model the turbulent flow between two infinitely wide 2D wavy plates at a bulk Reynolds number, Re_b=2800. We pursue two different but related flavors of analysis. The first one focuses on understanding the non-equilibrium near surface turbulence structure and the second one adopts a roughness characterization of such wavy surfaces. Analysis of the different statistical quantifications show strong dependence on wave slope for the roughness function indicating drag increase due to enhanced turbulent stresses resulting from increased production of vertical velocity variance from the surface undulations. Also, pronounced asymmetry is reported when comparing the turbulence structure on the upstream and downstream region of the wave. Advisors/Committee Members: Jayaraman, Balaji (advisor), Jacob, Jamey (committee member), San, Omer (committee member).

Subjects/Keywords: direct numerical simulation; roughness; wall turbulence; wavy surface

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APA (6^th Edition):

Khan, S. (2019). Near Wall Structure and Deviation from Equilibrium in Wavy Channel Turbulence. (Thesis). Oklahoma State University. Retrieved from http://hdl.handle.net/11244/323408

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Khan, Saadbin. “Near Wall Structure and Deviation from Equilibrium in Wavy Channel Turbulence.” 2019. Thesis, Oklahoma State University. Accessed January 17, 2021. http://hdl.handle.net/11244/323408.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Khan, Saadbin. “Near Wall Structure and Deviation from Equilibrium in Wavy Channel Turbulence.” 2019. Web. 17 Jan 2021.

Vancouver:

Khan S. Near Wall Structure and Deviation from Equilibrium in Wavy Channel Turbulence. [Internet] [Thesis]. Oklahoma State University; 2019. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11244/323408.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Khan S. Near Wall Structure and Deviation from Equilibrium in Wavy Channel Turbulence. [Thesis]. Oklahoma State University; 2019. Available from: http://hdl.handle.net/11244/323408

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

19. Edson Fernando Fumachi. Simulação do fluxo reacional de um reator de filamento quente através da simulação direta de Monte Carlo.

Degree: 2011, Instituto Nacional de Pesquisas Espaciais

URL: http://urlib.net/sid.inpe.br/mtc-m19/2011/01.13.19.15

►

Neste trabalho foi desenvolvido um modelo computacional para simular o ambiente gasoso presente em um reator de filamento quente na obtenção de filmes de diamante… (more)

▼

Neste trabalho foi desenvolvido um modelo computacional para simular o ambiente gasoso presente em um reator de filamento quente na obtenção de filmes de diamante através da deposição química à partir da fase gasosa. Foram estudados alguns mecanismos de crescimento aceitos pela comunidade científica e alguns modelos matemáticos de interação das espécies químicas bem como suas propriedades termodinâmicas. O modelo desenvolvido foi baseado na técnica DSMC que utiliza a distribuição de Maxwell-Boltzmann para a velocidade das partículas. Esse método é amplamente utilizado tanto na comunidade científica quanto na indústria com os propósitos mais variados. O modelo desenvolvido foi comparado com um expressivo trabalho da literatura e com resultados simulados através do pacote computacional CHEMKIN. Simulações adicionais foram realizadas a fim de verificarmos o comportamento do DSMCode quando submetidos à variações dos parâmetros de simulação. Os resultados obtidos estão em excelente concordância com os resultados experimentais e simulados por outros métodos creditando ao DSMCode uma ferramenta poderosa na simulação de um ambiente típico de reatores de filamento quente durante a produção de diamantes do tipo microcristalino.

In this work a computer model was developed to simulate the gaseous environment present in a hot filament reactor to obtain diamond films by chemical vapor deposition method. Some growth mechanisms were studied supported by the seientific community as well as some mathematical models of interaction of chemical species, associated to their thermodynamic properties. The model was based on DSMC technique that uses the Maxwell-Boltzmann distribution for the particle velocity. This method is widely used in both the scientific community and industry with the most varied purposes. The model was compared with a significant work of literature and with simulated results by CHEMKIN computer software. Additional simulations were conducted to verify the behavior of DSMCode for different simulation parameters. The results are in excellent agreement with the experimental and simulated data. DSMCode should to be a powerful tool to simulate a typical Hot Filament Chemical Vapor Deposition reactor for the production of microcrystalline diamond.

Advisors/Committee Members: Maurício Ribeiro Baldan, Neidenei Gomes Ferreira, João Fidélis Amstalden.

Subjects/Keywords: simulação numérica; Monte Carlo; diamante CVD; numerical simulation; direct simulation Monte Carlo-DSMC; CVD diamond

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Fumachi, E. F. (2011). Simulação do fluxo reacional de um reator de filamento quente através da simulação direta de Monte Carlo. (Thesis). Instituto Nacional de Pesquisas Espaciais. Retrieved from http://urlib.net/sid.inpe.br/mtc-m19/2011/01.13.19.15

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Fumachi, Edson Fernando. “Simulação do fluxo reacional de um reator de filamento quente através da simulação direta de Monte Carlo.” 2011. Thesis, Instituto Nacional de Pesquisas Espaciais. Accessed January 17, 2021. http://urlib.net/sid.inpe.br/mtc-m19/2011/01.13.19.15.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Fumachi, Edson Fernando. “Simulação do fluxo reacional de um reator de filamento quente através da simulação direta de Monte Carlo.” 2011. Web. 17 Jan 2021.

Vancouver:

Fumachi EF. Simulação do fluxo reacional de um reator de filamento quente através da simulação direta de Monte Carlo. [Internet] [Thesis]. Instituto Nacional de Pesquisas Espaciais; 2011. [cited 2021 Jan 17]. Available from: http://urlib.net/sid.inpe.br/mtc-m19/2011/01.13.19.15.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Fumachi EF. Simulação do fluxo reacional de um reator de filamento quente através da simulação direta de Monte Carlo. [Thesis]. Instituto Nacional de Pesquisas Espaciais; 2011. Available from: http://urlib.net/sid.inpe.br/mtc-m19/2011/01.13.19.15

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Minnesota

20. Liu, Jun. Advanced modeling of nanoparticle nucleation: towards the simulation of particle synthesis.

Degree: PhD, Mechanical Engineering, 2012, University of Minnesota

URL: http://purl.umn.edu/153850

► Nanotechnology holds a lot of promise for the discovery of new phenomena, and many of the envisioned processes involve nanoparticles. These particles are found in… (more)

▼ Nanotechnology holds a lot of promise for the discovery of new phenomena, and many of the envisioned processes involve nanoparticles. These particles are found in chemical sensors, drug targeting and delivery, and one important application is motivated by the need of clean renewable energy sources. Gas-to-particle conversion in the form of homogeneous nucleation within flow systems plays a significant role in a variety of natural and industrial processes of nanoparticle synthesis. In this work, nucleation processes of several metal materials and dibutyl phthalate (DBP) nanoparticles in laminar and turbulent flows are investigated via direct numerical simulations (DNS). The flows consist of condensing vapor diluted in argon or nitrogen issuing into a cooler particle-free stream. DNS facilitates probing the interactive effects of fluid dynamics and nucleation in an accurate manner. The fluid, thermal and chemical fields are obtained by solving the Navier-Stokes, enthalpy, and mass transport equations. Nucleation is simulated via calibrated classical homogeneous nucleation models. Recently developed size dependent surface tension model offers increased accuracy in predicting metal particle nucleation. This approach is attractive in that it promises to be more accurate than the classical nucleation theory while maintaining much of its simplicity when coupling with fluid dynamics. The effects of turbulence on metal nucleation are also studied using fully resolved DNS to elucidate the effects of different stages of fluid mixing on metal particle nucleation. The effects of nucleation on fluid dynamics are investigated via DNS of DBP nucleation within both laminar and turbulent jet flows. The simulations provide a demonstration of how heat release affects the interactions of fluid dynamics and nucleation at different Reynolds numbers and particle formation rates. The results provide insights into the interaction of fluid, thermal transport and nanoparticle nucleation in various flows, which stimulate development of models that will allow engineers to optimize the fluid and thermal environments for industrial nanoparticle production. For brevity, specific conclusions are provided in each chapter.

Subjects/Keywords: Computational Fluid Dynamics (CFD); Direct Numerical Simulation (DNS); Modeling and Simulation; Nanoparticle; Turbulence

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Liu, J. (2012). Advanced modeling of nanoparticle nucleation: towards the simulation of particle synthesis. (Doctoral Dissertation). University of Minnesota. Retrieved from http://purl.umn.edu/153850

Chicago Manual of Style (16^th Edition):

Liu, Jun. “Advanced modeling of nanoparticle nucleation: towards the simulation of particle synthesis.” 2012. Doctoral Dissertation, University of Minnesota. Accessed January 17, 2021. http://purl.umn.edu/153850.

MLA Handbook (7^th Edition):

Liu, Jun. “Advanced modeling of nanoparticle nucleation: towards the simulation of particle synthesis.” 2012. Web. 17 Jan 2021.

Vancouver:

Liu J. Advanced modeling of nanoparticle nucleation: towards the simulation of particle synthesis. [Internet] [Doctoral dissertation]. University of Minnesota; 2012. [cited 2021 Jan 17]. Available from: http://purl.umn.edu/153850.

Council of Science Editors:

Liu J. Advanced modeling of nanoparticle nucleation: towards the simulation of particle synthesis. [Doctoral Dissertation]. University of Minnesota; 2012. Available from: http://purl.umn.edu/153850

21. Martínez Ferrer, Pedro José. Étude par simulation numérique de l'auto-allumage en écoulement turbulent cisaillé supersonique : Numerical simulation of self-ignition in supersonic turbulent shear flow.

Degree: Docteur es, Energétique, thermique, combustion, 2013, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique

URL: http://www.theses.fr/2013ESMA0018

►

Cette étude est consacrée à l’analyse des écoulements réactifs supersoniques cisailléset, plus particulièrement, des couches de mélange compressibles pouvant se développerdans les moteurs ramjet et… (more)

▼

Cette étude est consacrée à l’analyse des écoulements réactifs supersoniques cisailléset, plus particulièrement, des couches de mélange compressibles pouvant se développerdans les moteurs ramjet et scramjet. Des méthodes numériques appropriées ont été implémentéeset vérifiées pour aboutir au développement d’un code de calcul numériquemassivement parallèle, appelé CREAMS (compressible reactive multi-species solver). Cedernier a été spécialement conçu pour conduire des simulations numériques haute précision(simulations numériques directes ou DNS) de ce type d’écoulements. Une attentionparticulière a été portée à la description des termes de transport moléculaire et des termessources chimiques de façon à considérer la description physique la plus fidèle possible desmélanges des gaz réactifs à haute vitesse, au sein desquelles les temps caractéristiqueschimiques et de mélange aux petites échelles sont susceptibles d’être du même ordre degrandeur. Les simulations des couches de mélange bidimensionnelles et tridimensionnelles,inertes et réactives, confirment l’importance des effets associés à la compressibilité et autaux de dégagement de chaleur. Les résultats ainsi obtenus diffèrent en certains points deceux issus d’autres simulations qui introduisaient certaines hypothèses simplificatrices :développement temporel, emploi d’une chimie globale ou encore lois de transport simplifiées.En revanche, ils reproduisent certains tendances déjà observées dans un certainnombre d’études expérimentales conduites dans des conditions similaires.

This study is devoted to the analysis of supersonic reactive shear flows and, in particular,compressible mixing layers that can develop inside the ramjet and scramjet engines.Appropriate numerical methods have been implemented and tested to achieve the developmentof a massively parallel numerical solver, called CREAMS (compressible reactivemulti-species solver). This tool was designed to conduct high-precision numerical simulations(direct numerical simulations or DNS) of such flows. Particular attention waspaid to the description of the molecular transport terms and chemical source terms toconsider the most accurate physical description of reactive gas mixtures at high velocity,in which the chemical and mixing time scales, corresponding to the smallest scalesof the flow, are susceptible to be of the same order of magnitude. Simulations of twoandthree-dimensional, inert and reactive, mixing layers confirm the importance of theeffects associated with compressibility and rate of heat release. The results obtained differin some points from other simulations which introduced simplifying assumptions such astemporal development, use of a global chemistry or a simplified description of the moleculartransport terms. Nevertheless, they reproduce some trends already observed in severalexperimental studies conducted under similar conditions.

Advisors/Committee Members: Mura, Arnaud (thesis director), Lehnasch, Guillaume (thesis director), Sabel'Nikov, Vladimir (thesis director).

Subjects/Keywords: Couche de mélange; Combustion supersonique; SImulation numérique directe; Mixing layer; Supersonic combustion; Direct numerical simulation

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Martínez Ferrer, P. J. (2013). Étude par simulation numérique de l'auto-allumage en écoulement turbulent cisaillé supersonique : Numerical simulation of self-ignition in supersonic turbulent shear flow. (Doctoral Dissertation). Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Retrieved from http://www.theses.fr/2013ESMA0018

Chicago Manual of Style (16^th Edition):

Martínez Ferrer, Pedro José. “Étude par simulation numérique de l'auto-allumage en écoulement turbulent cisaillé supersonique : Numerical simulation of self-ignition in supersonic turbulent shear flow.” 2013. Doctoral Dissertation, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Accessed January 17, 2021. http://www.theses.fr/2013ESMA0018.

MLA Handbook (7^th Edition):

Martínez Ferrer, Pedro José. “Étude par simulation numérique de l'auto-allumage en écoulement turbulent cisaillé supersonique : Numerical simulation of self-ignition in supersonic turbulent shear flow.” 2013. Web. 17 Jan 2021.

Vancouver:

Martínez Ferrer PJ. Étude par simulation numérique de l'auto-allumage en écoulement turbulent cisaillé supersonique : Numerical simulation of self-ignition in supersonic turbulent shear flow. [Internet] [Doctoral dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2013. [cited 2021 Jan 17]. Available from: http://www.theses.fr/2013ESMA0018.

Council of Science Editors:

Martínez Ferrer PJ. Étude par simulation numérique de l'auto-allumage en écoulement turbulent cisaillé supersonique : Numerical simulation of self-ignition in supersonic turbulent shear flow. [Doctoral Dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2013. Available from: http://www.theses.fr/2013ESMA0018

University of Southern California

22. Cadieux, Francois. Large eddy simulations of laminar separation bubble flows.

Degree: PhD, Aerospace and Mechanical Engineering (Computational Fluid and Solid Mechanics), 2015, University of Southern California

URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741

► The flow over blades and airfoils at moderate angles of attack and Reynolds numbers ranging from 10⁴ to 10⁵ undergoes separation due to the adverse… (more)

▼ The flow over blades and airfoils at moderate angles of attack and Reynolds numbers ranging from 10⁴ to 10⁵ undergoes separation due to the adverse pressure gradient generated by surface curvature. In many cases, the separated shear layer then transitions to turbulence and reattaches, closing off a recirculation region—the laminar separation bubble. To avoid body‐fitted mesh generation problems and numerical issues, an equivalent problem for flow over a flat plate is formulated by imposing boundary conditions that lead to a pressure distribution and Reynolds number that are similar to those on airfoils. Spalart & Strelets (2000) tested a number of Reynolds‐averaged Navier‐Stokes (RANS) turbulence models for a laminar separation bubble flow over a flat plate. Although results with the Spalart‐Allmaras turbulence model were encouraging, none of the turbulence models tested reliably recovered time‐averaged direct numerical simulation (DNS) results. The purpose of this work is to assess whether large eddy simulation (LES) can more accurately and reliably recover DNS results using drastically reduced resolution—on the order of 1% of DNS resolution which is commonly achievable for LES of turbulent channel flows. LES of a laminar separation bubble flow over a flat plate are performed using a compressible sixth‐order finite‐difference code and two incompressible pseudo‐spectral Navier‐Stokes solvers at resolutions corresponding to approximately 3% and 1% of the chosen DNS benchmark by Spalart & Strelets (2000). The finite‐difference solver is found to be dissipative due to the use of a stability‐enhancing filter. Its numerical dissipation is quantified and found to be comparable to the average eddy viscosity of the dynamic Smagorinsky model, making it difficult to separate the effects of filtering versus those of explicit subgrid‐scale modeling. The negligible numerical dissipation of the pseudo‐spectral solvers allows an unambiguous assessment of the performance of subgrid‐scale models. Three explicit subgrid‐scale models—dynamic Smagorinsky, σ, and truncated Navier‐Stokes (TNS)—are compared to a no‐model simulation (under‐resolved DNS) and evaluated against the benchmark DNS data focusing on two quantities of critical importance to airfoil and blade designers: time‐averaged pressure and skin friction predictions used in lift and drag calculations. Results obtained with these explicit subgrid‐scale models confirm that accurate LES of laminar separation bubble flows are attainable with as low as 1% of DNS resolution, and the poor performance of the no‐model simulation underscores the necessity of subgrid‐scale modelling in coarse LES with low numerical dissipation. Advisors/Committee Members: Domaradzki, Julian A. (Committee Chair), Spedding, Geoffrey R. (Committee Member), Redekopp, Larry G. (Committee Member), Lynett, Patrick J. (Committee Member), Becker, Thorsten W. (Committee Member).

Subjects/Keywords: computational fluid dynamics; fluid mechanics; direct numerical simulation; large eddy simulation; turbomachinery; UAV

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Cadieux, F. (2015). Large eddy simulations of laminar separation bubble flows. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741

Chicago Manual of Style (16^th Edition):

Cadieux, Francois. “Large eddy simulations of laminar separation bubble flows.” 2015. Doctoral Dissertation, University of Southern California. Accessed January 17, 2021. http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741.

MLA Handbook (7^th Edition):

Cadieux, Francois. “Large eddy simulations of laminar separation bubble flows.” 2015. Web. 17 Jan 2021.

Vancouver:

Cadieux F. Large eddy simulations of laminar separation bubble flows. [Internet] [Doctoral dissertation]. University of Southern California; 2015. [cited 2021 Jan 17]. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741.

Council of Science Editors:

Cadieux F. Large eddy simulations of laminar separation bubble flows. [Doctoral Dissertation]. University of Southern California; 2015. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741

University of Maryland

23. Verma, Salman. Understanding flame structure in wildfires using Large Eddy Simulations.

Degree: Fire Protection Engineering, 2014, University of Maryland

URL: http://hdl.handle.net/1903/16122

► The structure of wildfire flames in the presence of crossflow was analyzed by utilizing suitable non-reacting numerical experiments with low speed flow over a hot… (more)

Subjects/Keywords: Engineering; Direct Numerical Simulation; Large Eddy Simulation; Longitudinal vortices; OpenFOAM; Thermal instability; Wildfire spread

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APA (6^th Edition):

Verma, S. (2014). Understanding flame structure in wildfires using Large Eddy Simulations. (Thesis). University of Maryland. Retrieved from http://hdl.handle.net/1903/16122

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Verma, Salman. “Understanding flame structure in wildfires using Large Eddy Simulations.” 2014. Thesis, University of Maryland. Accessed January 17, 2021. http://hdl.handle.net/1903/16122.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Verma, Salman. “Understanding flame structure in wildfires using Large Eddy Simulations.” 2014. Web. 17 Jan 2021.

Vancouver:

Verma S. Understanding flame structure in wildfires using Large Eddy Simulations. [Internet] [Thesis]. University of Maryland; 2014. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1903/16122.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Verma S. Understanding flame structure in wildfires using Large Eddy Simulations. [Thesis]. University of Maryland; 2014. Available from: http://hdl.handle.net/1903/16122

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

24. Li, Cuicui. Analyse a-priori de modèles LES sous-mailles appliqués à la turbulence de paroi avec gradients de pression : A-priori analysis of LES subgrid scale models applied to wall turbulence with pressure gradients.

Degree: Docteur es, Mécanique, 2013, Ecole centrale de Lille

URL: http://www.theses.fr/2013ECLI0017

►

Après plus de 50 ans de recherche, l'intérêt de la simulation des grandes échelles pour la simulation des écoulements instationnaires a été largement démontré et… (more)

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Après plus de 50 ans de recherche, l'intérêt de la simulation des grandes échelles pour la simulation des écoulements instationnaires a été largement démontré et cette méthode est aujourd'hui utilisée pour une grande variété d'applications industrielles. Plusieurs classes de modèles sous-maille ont été proposées dont celle très connue des modèles de viscosité sous-maille souvent préférée pour sa simplicité et sa robustesse. Leur formulation comporte un coefficient qui doit être ajusté pour chaque type d'écoulement et qui a été analysé pour des géométries simples. L'objectif de ce travail est de réaliser des analyses a-priori de ces modèles dans un canal plan et un canal convergent-divergent à relativement grand nombre de Reynolds. Les influences du type de filtre et de la largeur du filtre sont systématiquement abordées pour chacune des statistiques. Le transfert d'énergie sous-maille et la dissipation sous-maille sont tout d'abord étudiés. Ensuite, les coefficients des modèles Smagorinsky, Smagorinsky dynamique, WALE et du modèle Sigma nouvellement proposé sont estimés a-priori. Il est démontré que les coefficients des quatre modèles sont non-homogènes dans le domaine de simulation et sont largement affectés par le gradient de pression adverse, principalement dans la zone de recirculation. Enfin, les corrélations entre les quantités exactes et leurs équivalents modélisés sont examinées. Les résultats montrent un faible niveau de prédiction des modèles sous-maille et une grande variabilité des quantités modélisées dans les régions de fort gradient de pression adverse. Ceci peut expliquer les difficultés pour obtenir de bons résultats LES dans une telle configuration

After more than 50 years of investigation, Large Eddy Simulation has demonstrated its benefit for unsteady flow simulation and is currently applied in a wide variety of engineering applications. Several classes of subgrid scale models were proposed, including the well known eddy viscosity models, usually preferred because of their simplicities and robustness. The formulation of these models includes a coefficient which needs to be analyzed for each flow configuration and which has been investigated in simple geometries.The aim of the present work is to perform a-priori analysis of subgrid scale models in plane channel flow and in a converging-diverging channel flow at fairly large Reynolds number.The influences of the filter type and filter width are systematically addressed in analyses of all statistics. The SGS energy transfer and energy dissipation are firstly analyzed.Then, the a priori estimate of the coefficients of subgrid scale models, including the standard Smagorinsky, Dynamic Smagorinsky, the WALE and the new updated sigma models, are investigated in detail. It is shown that, the coefficients of the four models are non-homogeneous in the simulation domain and are largely affected by the adverse pressure gradient, especially in the recirculation region. Finally, the correlations between the exact quantities and their counterparts modeled by…

Advisors/Committee Members: Stanislas, Michel (thesis director), Laval, Jean-Philippe (thesis director).

Subjects/Keywords: Simulation des grandes échelles; Turbulence; Filtrage; Simulation numérique directe; Large Eddy Simulation; Turbulence; Filter; Direct numerical simulation

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Li, C. (2013). Analyse a-priori de modèles LES sous-mailles appliqués à la turbulence de paroi avec gradients de pression : A-priori analysis of LES subgrid scale models applied to wall turbulence with pressure gradients. (Doctoral Dissertation). Ecole centrale de Lille. Retrieved from http://www.theses.fr/2013ECLI0017

Chicago Manual of Style (16^th Edition):

Li, Cuicui. “Analyse a-priori de modèles LES sous-mailles appliqués à la turbulence de paroi avec gradients de pression : A-priori analysis of LES subgrid scale models applied to wall turbulence with pressure gradients.” 2013. Doctoral Dissertation, Ecole centrale de Lille. Accessed January 17, 2021. http://www.theses.fr/2013ECLI0017.

MLA Handbook (7^th Edition):

Li, Cuicui. “Analyse a-priori de modèles LES sous-mailles appliqués à la turbulence de paroi avec gradients de pression : A-priori analysis of LES subgrid scale models applied to wall turbulence with pressure gradients.” 2013. Web. 17 Jan 2021.

Vancouver:

Li C. Analyse a-priori de modèles LES sous-mailles appliqués à la turbulence de paroi avec gradients de pression : A-priori analysis of LES subgrid scale models applied to wall turbulence with pressure gradients. [Internet] [Doctoral dissertation]. Ecole centrale de Lille; 2013. [cited 2021 Jan 17]. Available from: http://www.theses.fr/2013ECLI0017.

Council of Science Editors:

Li C. Analyse a-priori de modèles LES sous-mailles appliqués à la turbulence de paroi avec gradients de pression : A-priori analysis of LES subgrid scale models applied to wall turbulence with pressure gradients. [Doctoral Dissertation]. Ecole centrale de Lille; 2013. Available from: http://www.theses.fr/2013ECLI0017

King Abdullah University of Science and Technology

25. Khamedov, Ruslan. A Computational Study of Ammonia Combustion.

Degree: 2020, King Abdullah University of Science and Technology

URL: http://hdl.handle.net/10754/663983

► The utilization of ammonia as a fuel is a pragmatic approach to pave the way towards a low-carbon economy. Ammonia compromises almost 18 % of… (more)

▼ The utilization of ammonia as a fuel is a pragmatic approach to pave the way towards a low-carbon economy. Ammonia compromises almost 18 % of hydrogen by mass and accepted as one of the hydrogen combustion enablers with existing infrastructure for transportation and storage. From an environmental and sustainability standpoint, ammonia combustion is an attractive energy source with zero carbon dioxide emissions. However, from a practical point of view, the direct combustion of ammonia is not feasible due to the low reactive nature of ammonia. Due to the low combustion intensity, and the higher nitrogen oxide emission, ammonia was not fully investigated and there is still a lack of fundamental knowledge of ammonia combustion. In this thesis, the computational study of ammonia premixed flame characteristics under various hydrogen addition ratios and moderate or intense low oxygen dilution (MILD) conditions were investigated. Particularly, the heat release characteristics and dominant reaction pathways were analyzed. The analysis revealed that the peak of heat release for ammonia flame occurs near burned gas, which raises a question regarding the physics of this. Further analysis identified the dominant reaction pathways and the intermediate species (NH2 and OH), which are mainly produced in the downstream and back diffused to the leading edge and produce some heat in the low-temperature zone. To overcome low reactivity and poor combustion performance of pure ammonia mixture, the onboard ammonia decomposition to hydrogen and nitrogen followed by blending ammonia with hydrogen is a feasible approach to improve ammonia combustion intensity. With increasing hydrogen amount in the mixture, the enhancement of heat release occurs due to both transport and chemical effect of hydrogen. Another approach to mitigate the low reactive nature of ammonia may be eliminated by applying the promising combustion concept known as MILD combustion. The heat release characteristics and flame marker of ammonia turbulent premixed MILD combustion were investigated. The high fidelity numerical simulation was performed to answer fundamental questions of ammonia turbulent premixed combustion characteristics.

Subjects/Keywords: ammonia combustion; carbon-free fuel; Direct numerical simulation; heat release rate; numerical simulation; turbulent premixed combustion

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APA (6^th Edition):

Khamedov, R. (2020). A Computational Study of Ammonia Combustion. (Thesis). King Abdullah University of Science and Technology. Retrieved from http://hdl.handle.net/10754/663983

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Khamedov, Ruslan. “A Computational Study of Ammonia Combustion.” 2020. Thesis, King Abdullah University of Science and Technology. Accessed January 17, 2021. http://hdl.handle.net/10754/663983.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Khamedov, Ruslan. “A Computational Study of Ammonia Combustion.” 2020. Web. 17 Jan 2021.

Vancouver:

Khamedov R. A Computational Study of Ammonia Combustion. [Internet] [Thesis]. King Abdullah University of Science and Technology; 2020. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10754/663983.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Khamedov R. A Computational Study of Ammonia Combustion. [Thesis]. King Abdullah University of Science and Technology; 2020. Available from: http://hdl.handle.net/10754/663983

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Université Catholique de Louvain

26. Carton de Wiart, Corentin. Towards a Discontinuous Galerkin solver for scale-resolving simulations of moderate Reynolds number flows, and application to industrial cases.

Degree: 2014, Université Catholique de Louvain

URL: http://hdl.handle.net/2078.1/144023

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Due to the continuously increasing economical and environmental constraints, the standard industrial CFD methods (mostly Reynolds Averaged Navier-Stokes equations, RANS) are no longer sufficient to… (more)

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Due to the continuously increasing economical and environmental constraints, the standard industrial CFD methods (mostly Reynolds Averaged Navier-Stokes equations, RANS) are no longer sufficient to answer the design requirements of the industry, in particular when off-design performance and noise need to be predicted. Therefore, scale-resolving simulations, where the full (Direct Numerical Simulation, DNS) or at least a significant portion (Large-Eddy Simulation, LES) of the turbulence spectrum is resolved, are required. However, as these simulations require a nearly flawless representation of very small turbulent structures, current industrial solvers require huge computational resources in order to provide sufficient accuracy. The discontinuous Galerkin method (DGM) could alleviate this to a large extent as it seems to bridge the gap between the flexibility of industrial codes and the accuracy of academic solvers. During this thesis, the flexibility and the parallel efficiency of a DGM solver has been improved to tackle the large requirements of DNS and LES. The method was subsequently assessed for DNS and LES based on canonical benchmarks. Due to its interesting dissipation and dispersion properties, DGM seems to offer an accuracy similar to pseudo-spectral (PS) solvers for DNS. As the dissipation targets only the smallest scales, the method seems well suited to use an implicit LES approach. This approach has been validated on the simulation of homogeneous isotropic turbulence and on the channel flow at several Reynolds numbers. Finally, the method has been successfully applied on industrial cases, including a low pressure turbine blade, airfoil profiles and a high Mach number jet flow, thereby showing the maturity of the method.

(FSA - Sciences de l) – UCL, 2014

Advisors/Committee Members: UCL - SST/IMMC/TFL - Thermodynamics and fluid mechanics, UCL - SST/IMMC/MEMA - Applied mechanics and mathematics, UCL - Ecole Polytechnique de Louvain, Winckelmans, Grégoire, Remacle, Jean-François, Hillewaert, Koen, Bricteux, Laurent, Munz, Claus-Dieter, Chatelain, Philippe, Deleersnijder, Eric.

Subjects/Keywords: Discontinuous Galerkin Method; Scale-resolving simulation; Direct Numerical Simulation; (Implicit) Large Eddy Simulation; High Performance Computing; Computational Fluid Dynamics

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APA (6^th Edition):

Carton de Wiart, C. (2014). Towards a Discontinuous Galerkin solver for scale-resolving simulations of moderate Reynolds number flows, and application to industrial cases. (Thesis). Université Catholique de Louvain. Retrieved from http://hdl.handle.net/2078.1/144023

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Carton de Wiart, Corentin. “Towards a Discontinuous Galerkin solver for scale-resolving simulations of moderate Reynolds number flows, and application to industrial cases.” 2014. Thesis, Université Catholique de Louvain. Accessed January 17, 2021. http://hdl.handle.net/2078.1/144023.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Carton de Wiart, Corentin. “Towards a Discontinuous Galerkin solver for scale-resolving simulations of moderate Reynolds number flows, and application to industrial cases.” 2014. Web. 17 Jan 2021.

Vancouver:

Carton de Wiart C. Towards a Discontinuous Galerkin solver for scale-resolving simulations of moderate Reynolds number flows, and application to industrial cases. [Internet] [Thesis]. Université Catholique de Louvain; 2014. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2078.1/144023.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Carton de Wiart C. Towards a Discontinuous Galerkin solver for scale-resolving simulations of moderate Reynolds number flows, and application to industrial cases. [Thesis]. Université Catholique de Louvain; 2014. Available from: http://hdl.handle.net/2078.1/144023

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

27. Tronchin, Thibaut. Caractérisation expérimentale et numérique des mécanismes tourbillonnaires de génération de portance sur une aile en mouvement couplé de battement et tangage : Experimental and numerical characterization of vortex mechanisms of lift generation on a wing in flapping motion.

Degree: Docteur es, Mécanique des milieux fluides, 2013, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique

URL: http://www.theses.fr/2013ESMA0011

►

A bas nombre de Reynolds, le concept de voilure battante apparaît comme une alternative auxconcepts conventionnels de voilure fixe et voilure tournante. Dans le cadre… (more)

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A bas nombre de Reynolds, le concept de voilure battante apparaît comme une alternative auxconcepts conventionnels de voilure fixe et voilure tournante. Dans le cadre d’une applicationpratique (micro-drones ou MAVs), l’évaluation de l’adaptabilité d’un tel mode de sustentationrequiert la compréhension fine des principaux mécanismes aérodynamiques mis en jeu et de leurimpact sur les efforts résultants. Ces derniers se caractérisent par une instationnarité forte et descomportements complexes.Les travaux de cette thèse se concentrent sur l'étude du mouvement de vol battu à bas Reynolds (del'ordre de 1000), dans une configuration de vol stationnaire. Le modèle est constitué d’une ailerectangulaire à profil symétrique animé d’un mouvement couplé de battement et de tangage. Cemode de sustentation se caractérise par la génération à proximité de l'aile de structurestourbillonnaires plus ou moins persistantes influant fortement les efforts appliqués à l’aile.L'objectif consiste à analyser l'évolution des mécanismes instationnaires et des efforts en résultant.L'étude porte en particulier sur une analyse approfondie d'un cas de référence, comparé ensuite àd'autre résultats lors d'une étude paramétrique portant sur l’influences de l'allongement d'une part, etde la cinématique du mouvement d'autre part.Les moyens d’investigations adoptés pour mener cette étude sont à la fois numériques etexpérimentaux, L’analyse repose d’une part sur une approche numérique DNS utilisant unetechnique de maillage « chimère », et d’autre part sur des mesures en bassin de type PIV 3D-3Crésolues en temps. La mesure directe des efforts instationnaires de faible niveau étant difficilementenvisageable, une part importante du travail a consisté à adapter une méthode d’évaluation desefforts par bilan de quantité de mouvement à partir des champs de vitesse PIV résolus en temps. Lespoints durs de cette approche, en particulier l’évaluation de la pression à partir des champs devitesse, font l’objet d’une attention particulière.

A low Reynolds number, flapping wings appears as an alternative to conventional concepts of fixed wings and rotary wings aircrafts. In the context of a practical application (micro air vehicles, MAVs), assessing the suitability of such mode of lift generation requires a detailed understanding of the key aerodynamic mechanisms involved and their impact on resulting forces. These are characterized by a strong unsteadiness and complex behaviors.This work focuses on the study of flapping flight at low Reynolds (around 1 000), in a hover configuration. The model consists of a rectangular wing with a symmetrical profile in a flapping motion. This mode is characterized by the generation of vortex structures more or less persistent that strongly influence the forces applied to the wing.The objective is to analyze the evolution of unsteady mechanisms and resulting forces. The study focuses in particular on a thorough analysis of e reference case, then compared to other results in a parametric study on the influence of aspect-ratio on the one…

Advisors/Committee Members: Farcy, Alain (thesis director), David, Laurent (thesis director).

Subjects/Keywords: Vol battu; Piv 3d-3c; Simulaton numérique directe; Sustained flight; 3D PIV; Direct numerical simulation

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Tronchin, T. (2013). Caractérisation expérimentale et numérique des mécanismes tourbillonnaires de génération de portance sur une aile en mouvement couplé de battement et tangage : Experimental and numerical characterization of vortex mechanisms of lift generation on a wing in flapping motion. (Doctoral Dissertation). Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Retrieved from http://www.theses.fr/2013ESMA0011

Chicago Manual of Style (16^th Edition):

Tronchin, Thibaut. “Caractérisation expérimentale et numérique des mécanismes tourbillonnaires de génération de portance sur une aile en mouvement couplé de battement et tangage : Experimental and numerical characterization of vortex mechanisms of lift generation on a wing in flapping motion.” 2013. Doctoral Dissertation, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique. Accessed January 17, 2021. http://www.theses.fr/2013ESMA0011.

MLA Handbook (7^th Edition):

Tronchin, Thibaut. “Caractérisation expérimentale et numérique des mécanismes tourbillonnaires de génération de portance sur une aile en mouvement couplé de battement et tangage : Experimental and numerical characterization of vortex mechanisms of lift generation on a wing in flapping motion.” 2013. Web. 17 Jan 2021.

Vancouver:

Tronchin T. Caractérisation expérimentale et numérique des mécanismes tourbillonnaires de génération de portance sur une aile en mouvement couplé de battement et tangage : Experimental and numerical characterization of vortex mechanisms of lift generation on a wing in flapping motion. [Internet] [Doctoral dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2013. [cited 2021 Jan 17]. Available from: http://www.theses.fr/2013ESMA0011.

Council of Science Editors:

Tronchin T. Caractérisation expérimentale et numérique des mécanismes tourbillonnaires de génération de portance sur une aile en mouvement couplé de battement et tangage : Experimental and numerical characterization of vortex mechanisms of lift generation on a wing in flapping motion. [Doctoral Dissertation]. Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique; 2013. Available from: http://www.theses.fr/2013ESMA0011

University of California – San Diego

28. Nelson, Daniel Alan Wendell. High-Fidelity Lagrangian Coherent Structures Analysis and DNS with Discontinuous-Galerkin Methods.

Degree: Engineering Sciences (Mech and Aerospace Eng-Jt Doc SDSU), 2015, University of California – San Diego

URL: http://www.escholarship.org/uc/item/2cv4f732

► High-fidelity numerical tools based on high-order Discontinuous-Galerkin (DG) methods and Lagrangian Coherent Structure (LCS) theory are developed and validated for the study of separated, vortex-dominated… (more)

▼ High-fidelity numerical tools based on high-order Discontinuous-Galerkin (DG) methods and Lagrangian Coherent Structure (LCS) theory are developed and validated for the study of separated, vortex-dominated flows over complex geometry. The numerical framework couples prediction of separated turbulent flows using DG with time-dependent analysis of the flow through LCS and is intended for the development of separation control strategies for aerodynamic surfaces.The compressible viscous flow over a NACA 65-(1)412 airfoil is solved with a DG based Navier-Stokes solver in two and three dimensions. A method is presented in which high-order polynomial element edges adjacent to curved boundaries are matched to boundaries defined by non-smooth splines. Artificial surface roughness introduced by the piecewise-linear boundary approximation of straight-sided meshes results in the simulation of incorrect physics, including wake instabilities and spurious time-dependent modes. Spectral accuracy in the boundary approximation is not achieved for non-analytic boundary functions, particularly in high curvature regions.An algorithm is developed for the high-order computation of Finite-Time Lyapunov Exponent (FTLE) fields simultaneously and efficiently with two and three dimensional DG-based flow solvers. Fluid tracers are initialized at Gauss-Lobatto quadrature nodes within an element and form the high-order basis for a flow map at later time. Gradients of the flow map and FTLE are evaluated with DG operators. Multiple flow maps are determined from a single particle trace by remapping the flow map to the quadrature nodes on deformed mesh elements. For large integration times, excessive subdomain deformation deteriorates the interpolating conditioning. The conditioning provides information on the fluid deformation and identifies subdomains that contain LCS. An exponential filter smooths the flow map in highly deformed areas. The algorithm is tested on several benchmarks and is shown to have spectral convergence.The two and three-dimensional LCS field are analyzed for the unsteady flow over a NACA 65-(1)412 airfoil at a free-stream Reynolds number of Re=20,000 based on the chord length and a Mach number of 0.3. In two-dimensions, a Karman vortex street forms at the trailing edge. The three-dimensional vortex street breaks down to turbulence at the trailing edge.

Subjects/Keywords: Aerospace engineering; Direct Numerical Simulation; Discontinuous-Galerkin Methods; Lagrangian Coherent Structures; Spectral Methods

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APA (6^th Edition):

Nelson, D. A. W. (2015). High-Fidelity Lagrangian Coherent Structures Analysis and DNS with Discontinuous-Galerkin Methods. (Thesis). University of California – San Diego. Retrieved from http://www.escholarship.org/uc/item/2cv4f732

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Nelson, Daniel Alan Wendell. “High-Fidelity Lagrangian Coherent Structures Analysis and DNS with Discontinuous-Galerkin Methods.” 2015. Thesis, University of California – San Diego. Accessed January 17, 2021. http://www.escholarship.org/uc/item/2cv4f732.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Nelson, Daniel Alan Wendell. “High-Fidelity Lagrangian Coherent Structures Analysis and DNS with Discontinuous-Galerkin Methods.” 2015. Web. 17 Jan 2021.

Vancouver:

Nelson DAW. High-Fidelity Lagrangian Coherent Structures Analysis and DNS with Discontinuous-Galerkin Methods. [Internet] [Thesis]. University of California – San Diego; 2015. [cited 2021 Jan 17]. Available from: http://www.escholarship.org/uc/item/2cv4f732.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Nelson DAW. High-Fidelity Lagrangian Coherent Structures Analysis and DNS with Discontinuous-Galerkin Methods. [Thesis]. University of California – San Diego; 2015. Available from: http://www.escholarship.org/uc/item/2cv4f732

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Cornell University

29. McCaslin, Jeremy. Development And Application Of Numerical Methods For Interfacial Dynamics In Turbulent Liquid-Gas Flows.

Degree: PhD, Mechanical Engineering, 2015, Cornell University

URL: http://hdl.handle.net/1813/39359

► Liquid-gas flows are ubiquitous in both natural and engineering environments, and the processes that occur near the phase interface play a crucial role to the… (more)

▼ Liquid-gas flows are ubiquitous in both natural and engineering environments, and the processes that occur near the phase interface play a crucial role to the overall flow dynamics. When simulating such flows, the phase interface must be accurately tracked to allow for the handling of discontinuities in fluid properties and pressure. This work presents a level set-based interface capture technique that provides good mass conservation through the use of an auxiliary function. This function must be re-initialized to maintain mass conservation, and an approach for doing this in a way that minimizes re-initialization errors is presented. The resulting method is validated with a milk crown simulation, and it is shown that re-initialization errors in the form of spurious corrugations on the interface are removed from the simulation, leading to improved radial growth of the splashing lamella wall. The new method requires that numerical data be extrapolated from the interface to a band of cells surrounding it. This leads to the development of a framework for performing rapid multidimensional extrapolations that utilize a numerical procedure known as the fast marching method. Results demonstrate that when using this new framework, extrapolations with the same level of error can be obtained orders of magnitude faster than the current state-of-the-art. Applications of advanced numerical methods relevant to the energy sector are presented, including annular flows within horizontal pipes relevant to transport systems and air-assisted primary atomization of a three-dimensional planar liquid layer. For the former, simulations of fully turbulent liquid-gas pipe flows under various conditions are conducted, and the effect of the Froude number on the transition between the annular and stratified regimes is investigated. For the latter, a probability density function of the axial Kelvin-Helmholtz instability wavelength that arises due to shear between the initially parallel flows is extracted from the spatiotemporal data, and results are shown to agree well with experiments. Lastly, a canonical simulation configuration is developed that isolates the interaction between surface tension and surrounding turbulence. The Kolmogorov critical radius/Hinze scale is shown to be a controlling parameter for the resulting interface topology, as well as a source of backscatter of liquid volume fraction variance and kinetic energy from small to large scales. Advisors/Committee Members: Desjardins, Olivier (chair), Steen, Paul Herman (committee member), Warhaft, Zellman (committee member).

Subjects/Keywords: interfacial dynamics; liquid-gas flow; multiphase flow; interface capture; direct numerical simulation

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APA (6^th Edition):

McCaslin, J. (2015). Development And Application Of Numerical Methods For Interfacial Dynamics In Turbulent Liquid-Gas Flows. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/39359

Chicago Manual of Style (16^th Edition):

McCaslin, Jeremy. “Development And Application Of Numerical Methods For Interfacial Dynamics In Turbulent Liquid-Gas Flows.” 2015. Doctoral Dissertation, Cornell University. Accessed January 17, 2021. http://hdl.handle.net/1813/39359.

MLA Handbook (7^th Edition):

McCaslin, Jeremy. “Development And Application Of Numerical Methods For Interfacial Dynamics In Turbulent Liquid-Gas Flows.” 2015. Web. 17 Jan 2021.

Vancouver:

McCaslin J. Development And Application Of Numerical Methods For Interfacial Dynamics In Turbulent Liquid-Gas Flows. [Internet] [Doctoral dissertation]. Cornell University; 2015. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1813/39359.

Council of Science Editors:

McCaslin J. Development And Application Of Numerical Methods For Interfacial Dynamics In Turbulent Liquid-Gas Flows. [Doctoral Dissertation]. Cornell University; 2015. Available from: http://hdl.handle.net/1813/39359

Cornell University

30. Sukheswalla, Parvez. Computational Investigation Of The Dynamics Of Inertial Particles In Homogeneous Turbulent Shear Flow.

Degree: PhD, Mechanical Engineering, 2015, Cornell University

URL: http://hdl.handle.net/1813/40699

► Particle-laden turbulent shear flows are ubiquitous in environmental and industrial flow-systems, and their analysis is thus of prime importance. In this work, we study the… (more)

▼ Particle-laden turbulent shear flows are ubiquitous in environmental and industrial flow-systems, and their analysis is thus of prime importance. In this work, we study the motion of a dilute suspension of particles in a non-stationary homogeneous turbulent shear flow (HTSF), subject to varying levels of imposed mean-shear, gravity, and inertia. We use direct numerical simulations (DNS) of the fluid velocity field (coupled with Lagrangian particle tracking), to assess the influence of flow-anisotropy and gravity on the motion of the particles. We first discuss numerical challenges encountered while performing DNS of HTSF at higher Reynolds numbers. The presence of sharp velocity gradients in the HTSF flow field is found to cause premature loss of resolution at the small scales, leading to shortened simulation-times. To counter this, the existing pseudo-spectral DNS setup is augmented with a Weighted Essentially Non-Oscillatory (WENO) scheme, enabling numerically-stable HTSF simulations at higher Reynolds numbers. We then consider the motion of individual particles as they interact with the anisotropic topology of the turbulence. In contrast to isotropic turbulence, particles are found to collect within vortex layers, regions where strong vorticity and strain are coupled with low streamline curvature. Shear-induced anisotropy in the turbulence also leads to reduced gravitational settling speeds for intermediate-inertia particles, though stronger gravity overcomes this effect. Particle velocity variances are found to be highly anisotropic at stronger shear, while gravity now tends to diminish this effect by limiting the interaction-time between particles and turbulence. Shear and gravity acting together cause particle acceleration variances to exceed those of the underlying fluid, corroborating findings from past turbulent boundary layer experiments. Analytical expressions are derived for the mean velocities and accelerations of the particles, and are in agreement with the DNS results. Finally, we analyze the relative velocities and clustering characteristics of particle pairs, and find that stronger shear and gravity suppress path-history effects for particles with stronger inertia. Shear-induced anisotropy in pair-statistics is affected by both inertia and gravity, with stronger gravity seen to oppose the action of shear. Changes in the relative-velocity anisotropy are correlated to the trends shown by single-particle velocity variances. Particle collision rates increase with stronger shear, and are found to scale in proportion to the underlying turbulence timescales.

Subjects/Keywords: Turbulent Shear Flow; Inertial Particles; Particle Clustering; Anisotropy; Direct Numerical Simulation; WENO Scheme

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Sukheswalla, P. (2015). Computational Investigation Of The Dynamics Of Inertial Particles In Homogeneous Turbulent Shear Flow. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/40699

Chicago Manual of Style (16^th Edition):

Sukheswalla, Parvez. “Computational Investigation Of The Dynamics Of Inertial Particles In Homogeneous Turbulent Shear Flow.” 2015. Doctoral Dissertation, Cornell University. Accessed January 17, 2021. http://hdl.handle.net/1813/40699.

MLA Handbook (7^th Edition):

Sukheswalla, Parvez. “Computational Investigation Of The Dynamics Of Inertial Particles In Homogeneous Turbulent Shear Flow.” 2015. Web. 17 Jan 2021.

Vancouver:

Sukheswalla P. Computational Investigation Of The Dynamics Of Inertial Particles In Homogeneous Turbulent Shear Flow. [Internet] [Doctoral dissertation]. Cornell University; 2015. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1813/40699.

Council of Science Editors:

Sukheswalla P. Computational Investigation Of The Dynamics Of Inertial Particles In Homogeneous Turbulent Shear Flow. [Doctoral Dissertation]. Cornell University; 2015. Available from: http://hdl.handle.net/1813/40699

Open Access Theses and Dissertations