Dennis Lankford - Academia.edu (original) (raw)

Papers by Dennis Lankford

Powder Technology, May 1, 2012

A continuous random walk (CRW) turbulent diffusion model was adapted for Lagrangian particles wit... more A continuous random walk (CRW) turbulent diffusion model was adapted for Lagrangian particles within gas flowfields simulated by hybrid RANS/LES methodologies. The methodology was designed to model all the particle diffusion in RANS regions and model only the sub-grid diffusion in LES regions. In the RANS approach, the mean flowfield and the turbulent time-and length-scales are obtained with a k-ω (Menter SST) turbulence model. These values are used with a discrete stochastic equation to compute instantaneous gas velocity along an individual particle trajectory. Experimental results for turbulent diffusion of particles in a homogeneous wake flow were first used to calibrate the RANS model. The stochastic diffusion model was then extended to utilize the Nichols-Nelson k-ω hybrid RANS/LES turbulence model in the unsteady three-dimensional wake of a cylinder. In particular, the flow at a Mach number of 0.1 and Reynolds number (Re D) of 800 was computed with a 5th-order upwind-biased scheme. The discrete stochastic equation was used to compute sub-grid fluctuations, which could be added to the resolved velocity field, and specifically took into account combined effects of particle inertia and non-homogeneous turbulence. The combination of resolved diffusion and sub-grid diffusion compared quite reasonably with diffusion based on Direct Numerical Simulation of the Navier-Stokes equations. The results indicate that eddy-crossing effects and inertia-based drift corrections can be critical, even when most of the kinetic energy is captured with the resolved-scales of an LES approach.

This book contains the proceedings of numerical methods in multiphase flows. Topics covered inclu... more This book contains the proceedings of numerical methods in multiphase flows. Topics covered include: Turbulent Flow; Fluidized-bed Hydrodynamic; Nozzles; Two-Phase Flow.

Pitot pressure may be used as a measure of stream thrust in supersonic reacting flows. Previous w... more Pitot pressure may be used as a measure of stream thrust in supersonic reacting flows. Previous work has assumed ideal, perfect gas behavior. This paper extends the analysis to chemically reacting flow. The effect of probe size on the measured pitot pressure is explored. Large probe sizes produce higher pitot pressure than smaller probes. However, even the largest probe sizes do not approach the chemical equilibrium pitot pressure limit because of entropy generation behind the shock attributable to finite-rate chemical reactions. Small probe sizes do approach the frozen chemistry pitot pressure limit. The frozen and equilibrium limits are separated by approximately 10 percent, but the pitot pressures computed with finite-rate chemistry varies less than 3 percent regardless of probe size. This reduces the uncertainty associated with inferring stream thrust from pitot pressure measurements in reacting flows. Conditions typical of a typical storable propellant rocket are considered. These calculations will guide the choice of probe sizes in reacting flows, and provide an indication of the uncertainty associated with inferring stream thrust from pitot pressure in reacting flows.

Computers & Fluids, 2009

An algorithm has been developed to efficiently determine the correct particle host cell for unstr... more An algorithm has been developed to efficiently determine the correct particle host cell for unstructured grids with multiple element types (e.g. tetrahedrons, prisms, hexahedrons, etc.) and large particle movements (e.g. movement across single or multiple cells). The algorithm utilizes a ''dot product" searching technique where a direction vector connecting a face centroid and the particle location is dotted with an outwardly-positive face normal to facilitate the host cell search. The algorithm is investigated for particles moving a distance of one or several cell lengths on a variety of two-dimensional (2-D) and three-dimensional (3-D) meshes. Two variations of this approach are introduced and tested, each focusing on different strategies (cell-searching vs. face-searching minimization) to optimize the use of computational resources. Finally, in order to increase the efficiency of each algorithm in the case of large problems where the previous host cell is not known, a ''coarse-grain" search is introduced, whereby a small sampling of the total cells are inspected, after which the adjoining-faces search is completed in the host sub-domain.

34th Aerospace Sciences Meeting and Exhibit, Jan 15, 1996

The objective of this study was to implement and test a computational methodology involving NPARC... more The objective of this study was to implement and test a computational methodology involving NPARC and a modified KIVA-II code (K-ICE), designed for robust and accurate prediction of spray bar droplet dispersion for aeropropulsion icing tests. A validation study was completed to test the stochastic eddy model for turbulent dispersion calculations. This involved a particle dispersion experimental data set in a gridgenerated turbulence field for which turbulent time scale coefficients used in the dispersion calculations were calibrated. Parametric studies were then completed on a partial domain of an NPARC air flow field solution for the AEDC ASTF test cell. The parametric studies tested computational, spray, vapor and tunnel parameters. Results from this partial domain study show several trends based on liquid water content (LWC) uniformity, including the strong sensitivity to the turbulent time scale coefficients, turbulent kinetic energy, and initial droplet velocity and temperature. Next, two calculations were performed on the full ASTF domain solution based on two different nozzle configurations. Among the conclusions drawn from this study are that LWC distributions at the test section can exhibit significant non-uniformity based on high spatial resolution predictions. Finally, a novel acceleration scheme was formulated and successfully tested, achieving reductions in computational resources of an order of magnitude.

38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit

Pitot pressure may be used as a measure of stream thrust in supersonic reacting flows. Previous w... more Pitot pressure may be used as a measure of stream thrust in supersonic reacting flows. Previous work has assumed ideal, perfect gas behavior. This paper extends the analysis to chemically reacting flow. The effect of probe size on the measured pitot pressure is explored. Large probe sizes produce higher pitot pressure than smaller probes. However, even the largest probe sizes do not approach the chemical equilibrium pitot pressure limit because of entropy generation behind the shock attributable to finite-rate chemical reactions. Small probe sizes do approach the frozen chemistry pitot pressure limit. The frozen and equilibrium limits are separated by approximately 10 percent, but the pitot pressures computed with finite-rate chemistry varies less than 3 percent regardless of probe size. This reduces the uncertainty associated with inferring stream thrust from pitot pressure measurements in reacting flows. Conditions typical of a typical storable propellant rocket are considered. These calculations will guide the choice of probe sizes in reacting flows, and provide an indication of the uncertainty associated with inferring stream thrust from pitot pressure in reacting flows.

The Wind-US flow solver has been modified to include real gas thermodynamic properties and real g... more The Wind-US flow solver has been modified to include real gas thermodynamic properties and real gas fluxes of conserved variables. The real gas evaluations relevant to a specific molecule have been isolated to a single subroutine so that any substances can be implemented relatively easily. Molecular nitrogen and hydrogen have been implemented in the program to date. The real gas model has been implemented in the Wind-US Roe approximate Riemann solver at this time. The real gas nitrogen model has been used to predict converging-diverging nozzle flow at total pressures ranging from nominally 250 to 20,000 psi at a nominal stagnation temperature of 3000oR and exit Mach numbers of 8 to 14. A comparison of the 20,000-psi results with data is presented in this paper. The real gas hydrogen model is used to model high-pressure shock tube calculations relevant to analysis of light gas hypervelocity gun range facilities. I.

When US Goverroent drawings, specifications, or othee data are used for any purpose other than a ... more When US Goverroent drawings, specifications, or othee data are used for any purpose other than a definitely related Government procurement operation, the Government thereby incurs no responsibility nor aty obligation whatsoever, and the fact that the Government way have formulated, furnished, cir in any way supplied the said drawings, specifications, cr other data, is not to be regarded by impltcaticn or otherwise, as in any manner licensing the holder or any other person or corporaticn, or conveying any rights or permission to iranufacture, use, or sell any patentee invention that m)y in any way be related thereto.

2018 Applied Aerodynamics Conference, 2018

2018 Applied Aerodynamics Conference, 2018

This book contains the proceedings of numerical methods in multiphase flows. Topics covered inclu... more This book contains the proceedings of numerical methods in multiphase flows. Topics covered include: Turbulent Flow; Fluidized-bed Hydrodynamic; Nozzles; Two-Phase Flow.

44th AIAA Aerospace Sciences Meeting and Exhibit, 2006

A simulation capability for turbulent dispersed multiphase flows was developed and implemented wi... more A simulation capability for turbulent dispersed multiphase flows was developed and implemented within WIND-US employing both structured boundary fitted meshes and unstructured meshes. The approach is based on a Reynolds-Averaged Navier-Stokes (RANS) Eulerian approach for the continuous fluid phase. A Continuous Random Walk (CRW) model was developed and implemented into WIND-US to model the turbulent velocity fluctuations seen by the dispersed phase as a stochastic process. The resulting code was then validated by simulations of a flow through a square duct section containing isotropic, homogenous turbulence consistent with measurements of turbulent particle diffusion by Snyder and Lumley. The simulations for both structured and unstructured meshes show good correlation between WIND-US and Snyder and Lumley's experimental data. Nomenclature a Speed of sound c Λ Eddy length scale coefficient c µ Turbulence length scale coefficient c τ Eddy time scale coefficient d Droplet diameter f Stokes correction factor g Gravitational acceleration k Turbulent kinetic energy M Mach number m Mass Re Reynolds number St Stokes number t Time u Fluid velocity v Particle velocity w Relative velocity x Particle position Turbulent dissipation γ Random Gaussian number Λ Integral length scale * The research reported herein was performed for the Arnold Engineering Development Center(AEDC), Air Force Materiel Command. Work and analysis for this research were performed by personnel of the University of Illinois at Urbana-Champagne and by personnel of Aerospace Testing Alliance, the operations, maintenance, information management, and support contractor for AEDC. † M.S. Student, Aerospace Engineering, AIAA member. ‡ Professor,Aerospace Engineering, AIAA member. § AIAA senior member.

Abstract : The electron collision frequency is a critical parameter in determining the attenuatio... more Abstract : The electron collision frequency is a critical parameter in determining the attenuation of electromagnetic signals transmitted through the plasma sheath surrounding advanced reentry vehicles. This study improves current methods of obtaining this parameter for multicomponent gas mixtures. A multicomponent collision frequency model is defined with temperature and species-dependent electron collision cross sections. A parametric study of collision frequency in a gaseous mixture of phenolic carbon and air is performed using this model, and the results are compared to calculations made using a constant cross-section, clean air model. A study of collision frequency and signal attenuation in turbulent boundary layers is performed using the multicomponent and constant cross-section models. This study shows that the multicomponent model can predict collisions frequencies in an ablation air mixture that are significantly different from those predicted by constant cross- section models.

31st Aerospace Sciences Meeting, 1993

43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005

The Wind-US flow solver has been modified to include real gas thermodynamic properties and real g... more The Wind-US flow solver has been modified to include real gas thermodynamic properties and real gas fluxes of conserved variables. The real gas evaluations relevant to a specific molecule have been isolated to a single subroutine so that any substances can be implemented relatively easily. Molecular nitrogen and hydrogen have been implemented in the program to date. The real gas model has been implemented in the Wind-US Roe approximate Riemann solver at this time. The real gas nitrogen model has been used to predict converging-diverging nozzle flow at total pressures ranging from nominally 250 to 20,000 psi at a nominal stagnation temperature of 3000 o R and exit Mach numbers of 8 to 14. A comparison of the 20,000-psi results with data is presented in this paper. The real gas hydrogen model is used to model high-pressure shock tube calculations relevant to analysis of light gas hypervelocity gun range facilities. * The research reported herein was performed by the Arnold Engineering Development Center (AEDC), Air Force Materiel Command. Work and analysis for this research were performed by personnel of Aerospace Testing Alliance, the operations, maintenance, information management, and support contractor for AEDC. Further reproduction is authorized to satisfy needs of the U. S. Government. † Senior Member, AIAA. ‡ Associate Fellow, AIAA.

29th Aerospace Sciences Meeting, 1991

34th Aerospace Sciences Meeting and Exhibit, 1996

The objective of this study was to implement and test a computational methodology involving NPARC... more The objective of this study was to implement and test a computational methodology involving NPARC and a modified KIVA-II code (K-ICE), designed for robust and accurate prediction of spray bar droplet dispersion for aeropropulsion icing tests. A validation study was completed to test the stochastic eddy model for turbulent dispersion calculations. This involved a particle dispersion experimental data set in a gridgenerated turbulence field for which turbulent time scale coefficients used in the dispersion calculations were calibrated. Parametric studies were then completed on a partial domain of an NPARC air flow field solution for the AEDC ASTF test cell. The parametric studies tested computational, spray, vapor and tunnel parameters. Results from this partial domain study show several trends based on liquid water content (LWC) uniformity, including the strong sensitivity to the turbulent time scale coefficients, turbulent kinetic energy, and initial droplet velocity and temperature. Next, two calculations were performed on the full ASTF domain solution based on two different nozzle configurations. Among the conclusions drawn from this study are that LWC distributions at the test section can exhibit significant non-uniformity based on high spatial resolution predictions. Finally, a novel acceleration scheme was formulated and successfully tested, achieving reductions in computational resources of an order of magnitude.

46th AIAA Aerospace Sciences Meeting and Exhibit, 2008

16th Thermophysics Conference, 1981

Powder Technology, May 1, 2012

A continuous random walk (CRW) turbulent diffusion model was adapted for Lagrangian particles wit... more A continuous random walk (CRW) turbulent diffusion model was adapted for Lagrangian particles within gas flowfields simulated by hybrid RANS/LES methodologies. The methodology was designed to model all the particle diffusion in RANS regions and model only the sub-grid diffusion in LES regions. In the RANS approach, the mean flowfield and the turbulent time-and length-scales are obtained with a k-ω (Menter SST) turbulence model. These values are used with a discrete stochastic equation to compute instantaneous gas velocity along an individual particle trajectory. Experimental results for turbulent diffusion of particles in a homogeneous wake flow were first used to calibrate the RANS model. The stochastic diffusion model was then extended to utilize the Nichols-Nelson k-ω hybrid RANS/LES turbulence model in the unsteady three-dimensional wake of a cylinder. In particular, the flow at a Mach number of 0.1 and Reynolds number (Re D) of 800 was computed with a 5th-order upwind-biased scheme. The discrete stochastic equation was used to compute sub-grid fluctuations, which could be added to the resolved velocity field, and specifically took into account combined effects of particle inertia and non-homogeneous turbulence. The combination of resolved diffusion and sub-grid diffusion compared quite reasonably with diffusion based on Direct Numerical Simulation of the Navier-Stokes equations. The results indicate that eddy-crossing effects and inertia-based drift corrections can be critical, even when most of the kinetic energy is captured with the resolved-scales of an LES approach.

This book contains the proceedings of numerical methods in multiphase flows. Topics covered inclu... more This book contains the proceedings of numerical methods in multiphase flows. Topics covered include: Turbulent Flow; Fluidized-bed Hydrodynamic; Nozzles; Two-Phase Flow.

Pitot pressure may be used as a measure of stream thrust in supersonic reacting flows. Previous w... more Pitot pressure may be used as a measure of stream thrust in supersonic reacting flows. Previous work has assumed ideal, perfect gas behavior. This paper extends the analysis to chemically reacting flow. The effect of probe size on the measured pitot pressure is explored. Large probe sizes produce higher pitot pressure than smaller probes. However, even the largest probe sizes do not approach the chemical equilibrium pitot pressure limit because of entropy generation behind the shock attributable to finite-rate chemical reactions. Small probe sizes do approach the frozen chemistry pitot pressure limit. The frozen and equilibrium limits are separated by approximately 10 percent, but the pitot pressures computed with finite-rate chemistry varies less than 3 percent regardless of probe size. This reduces the uncertainty associated with inferring stream thrust from pitot pressure measurements in reacting flows. Conditions typical of a typical storable propellant rocket are considered. These calculations will guide the choice of probe sizes in reacting flows, and provide an indication of the uncertainty associated with inferring stream thrust from pitot pressure in reacting flows.

Computers & Fluids, 2009

An algorithm has been developed to efficiently determine the correct particle host cell for unstr... more An algorithm has been developed to efficiently determine the correct particle host cell for unstructured grids with multiple element types (e.g. tetrahedrons, prisms, hexahedrons, etc.) and large particle movements (e.g. movement across single or multiple cells). The algorithm utilizes a ''dot product" searching technique where a direction vector connecting a face centroid and the particle location is dotted with an outwardly-positive face normal to facilitate the host cell search. The algorithm is investigated for particles moving a distance of one or several cell lengths on a variety of two-dimensional (2-D) and three-dimensional (3-D) meshes. Two variations of this approach are introduced and tested, each focusing on different strategies (cell-searching vs. face-searching minimization) to optimize the use of computational resources. Finally, in order to increase the efficiency of each algorithm in the case of large problems where the previous host cell is not known, a ''coarse-grain" search is introduced, whereby a small sampling of the total cells are inspected, after which the adjoining-faces search is completed in the host sub-domain.

34th Aerospace Sciences Meeting and Exhibit, Jan 15, 1996

The objective of this study was to implement and test a computational methodology involving NPARC... more The objective of this study was to implement and test a computational methodology involving NPARC and a modified KIVA-II code (K-ICE), designed for robust and accurate prediction of spray bar droplet dispersion for aeropropulsion icing tests. A validation study was completed to test the stochastic eddy model for turbulent dispersion calculations. This involved a particle dispersion experimental data set in a gridgenerated turbulence field for which turbulent time scale coefficients used in the dispersion calculations were calibrated. Parametric studies were then completed on a partial domain of an NPARC air flow field solution for the AEDC ASTF test cell. The parametric studies tested computational, spray, vapor and tunnel parameters. Results from this partial domain study show several trends based on liquid water content (LWC) uniformity, including the strong sensitivity to the turbulent time scale coefficients, turbulent kinetic energy, and initial droplet velocity and temperature. Next, two calculations were performed on the full ASTF domain solution based on two different nozzle configurations. Among the conclusions drawn from this study are that LWC distributions at the test section can exhibit significant non-uniformity based on high spatial resolution predictions. Finally, a novel acceleration scheme was formulated and successfully tested, achieving reductions in computational resources of an order of magnitude.

38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit

Pitot pressure may be used as a measure of stream thrust in supersonic reacting flows. Previous w... more Pitot pressure may be used as a measure of stream thrust in supersonic reacting flows. Previous work has assumed ideal, perfect gas behavior. This paper extends the analysis to chemically reacting flow. The effect of probe size on the measured pitot pressure is explored. Large probe sizes produce higher pitot pressure than smaller probes. However, even the largest probe sizes do not approach the chemical equilibrium pitot pressure limit because of entropy generation behind the shock attributable to finite-rate chemical reactions. Small probe sizes do approach the frozen chemistry pitot pressure limit. The frozen and equilibrium limits are separated by approximately 10 percent, but the pitot pressures computed with finite-rate chemistry varies less than 3 percent regardless of probe size. This reduces the uncertainty associated with inferring stream thrust from pitot pressure measurements in reacting flows. Conditions typical of a typical storable propellant rocket are considered. These calculations will guide the choice of probe sizes in reacting flows, and provide an indication of the uncertainty associated with inferring stream thrust from pitot pressure in reacting flows.

The Wind-US flow solver has been modified to include real gas thermodynamic properties and real g... more The Wind-US flow solver has been modified to include real gas thermodynamic properties and real gas fluxes of conserved variables. The real gas evaluations relevant to a specific molecule have been isolated to a single subroutine so that any substances can be implemented relatively easily. Molecular nitrogen and hydrogen have been implemented in the program to date. The real gas model has been implemented in the Wind-US Roe approximate Riemann solver at this time. The real gas nitrogen model has been used to predict converging-diverging nozzle flow at total pressures ranging from nominally 250 to 20,000 psi at a nominal stagnation temperature of 3000oR and exit Mach numbers of 8 to 14. A comparison of the 20,000-psi results with data is presented in this paper. The real gas hydrogen model is used to model high-pressure shock tube calculations relevant to analysis of light gas hypervelocity gun range facilities. I.

When US Goverroent drawings, specifications, or othee data are used for any purpose other than a ... more When US Goverroent drawings, specifications, or othee data are used for any purpose other than a definitely related Government procurement operation, the Government thereby incurs no responsibility nor aty obligation whatsoever, and the fact that the Government way have formulated, furnished, cir in any way supplied the said drawings, specifications, cr other data, is not to be regarded by impltcaticn or otherwise, as in any manner licensing the holder or any other person or corporaticn, or conveying any rights or permission to iranufacture, use, or sell any patentee invention that m)y in any way be related thereto.

2018 Applied Aerodynamics Conference, 2018

2018 Applied Aerodynamics Conference, 2018

This book contains the proceedings of numerical methods in multiphase flows. Topics covered inclu... more This book contains the proceedings of numerical methods in multiphase flows. Topics covered include: Turbulent Flow; Fluidized-bed Hydrodynamic; Nozzles; Two-Phase Flow.

44th AIAA Aerospace Sciences Meeting and Exhibit, 2006

A simulation capability for turbulent dispersed multiphase flows was developed and implemented wi... more A simulation capability for turbulent dispersed multiphase flows was developed and implemented within WIND-US employing both structured boundary fitted meshes and unstructured meshes. The approach is based on a Reynolds-Averaged Navier-Stokes (RANS) Eulerian approach for the continuous fluid phase. A Continuous Random Walk (CRW) model was developed and implemented into WIND-US to model the turbulent velocity fluctuations seen by the dispersed phase as a stochastic process. The resulting code was then validated by simulations of a flow through a square duct section containing isotropic, homogenous turbulence consistent with measurements of turbulent particle diffusion by Snyder and Lumley. The simulations for both structured and unstructured meshes show good correlation between WIND-US and Snyder and Lumley's experimental data. Nomenclature a Speed of sound c Λ Eddy length scale coefficient c µ Turbulence length scale coefficient c τ Eddy time scale coefficient d Droplet diameter f Stokes correction factor g Gravitational acceleration k Turbulent kinetic energy M Mach number m Mass Re Reynolds number St Stokes number t Time u Fluid velocity v Particle velocity w Relative velocity x Particle position Turbulent dissipation γ Random Gaussian number Λ Integral length scale * The research reported herein was performed for the Arnold Engineering Development Center(AEDC), Air Force Materiel Command. Work and analysis for this research were performed by personnel of the University of Illinois at Urbana-Champagne and by personnel of Aerospace Testing Alliance, the operations, maintenance, information management, and support contractor for AEDC. † M.S. Student, Aerospace Engineering, AIAA member. ‡ Professor,Aerospace Engineering, AIAA member. § AIAA senior member.

Abstract : The electron collision frequency is a critical parameter in determining the attenuatio... more Abstract : The electron collision frequency is a critical parameter in determining the attenuation of electromagnetic signals transmitted through the plasma sheath surrounding advanced reentry vehicles. This study improves current methods of obtaining this parameter for multicomponent gas mixtures. A multicomponent collision frequency model is defined with temperature and species-dependent electron collision cross sections. A parametric study of collision frequency in a gaseous mixture of phenolic carbon and air is performed using this model, and the results are compared to calculations made using a constant cross-section, clean air model. A study of collision frequency and signal attenuation in turbulent boundary layers is performed using the multicomponent and constant cross-section models. This study shows that the multicomponent model can predict collisions frequencies in an ablation air mixture that are significantly different from those predicted by constant cross- section models.

31st Aerospace Sciences Meeting, 1993

43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005

The Wind-US flow solver has been modified to include real gas thermodynamic properties and real g... more The Wind-US flow solver has been modified to include real gas thermodynamic properties and real gas fluxes of conserved variables. The real gas evaluations relevant to a specific molecule have been isolated to a single subroutine so that any substances can be implemented relatively easily. Molecular nitrogen and hydrogen have been implemented in the program to date. The real gas model has been implemented in the Wind-US Roe approximate Riemann solver at this time. The real gas nitrogen model has been used to predict converging-diverging nozzle flow at total pressures ranging from nominally 250 to 20,000 psi at a nominal stagnation temperature of 3000 o R and exit Mach numbers of 8 to 14. A comparison of the 20,000-psi results with data is presented in this paper. The real gas hydrogen model is used to model high-pressure shock tube calculations relevant to analysis of light gas hypervelocity gun range facilities. * The research reported herein was performed by the Arnold Engineering Development Center (AEDC), Air Force Materiel Command. Work and analysis for this research were performed by personnel of Aerospace Testing Alliance, the operations, maintenance, information management, and support contractor for AEDC. Further reproduction is authorized to satisfy needs of the U. S. Government. † Senior Member, AIAA. ‡ Associate Fellow, AIAA.

29th Aerospace Sciences Meeting, 1991

34th Aerospace Sciences Meeting and Exhibit, 1996

The objective of this study was to implement and test a computational methodology involving NPARC... more The objective of this study was to implement and test a computational methodology involving NPARC and a modified KIVA-II code (K-ICE), designed for robust and accurate prediction of spray bar droplet dispersion for aeropropulsion icing tests. A validation study was completed to test the stochastic eddy model for turbulent dispersion calculations. This involved a particle dispersion experimental data set in a gridgenerated turbulence field for which turbulent time scale coefficients used in the dispersion calculations were calibrated. Parametric studies were then completed on a partial domain of an NPARC air flow field solution for the AEDC ASTF test cell. The parametric studies tested computational, spray, vapor and tunnel parameters. Results from this partial domain study show several trends based on liquid water content (LWC) uniformity, including the strong sensitivity to the turbulent time scale coefficients, turbulent kinetic energy, and initial droplet velocity and temperature. Next, two calculations were performed on the full ASTF domain solution based on two different nozzle configurations. Among the conclusions drawn from this study are that LWC distributions at the test section can exhibit significant non-uniformity based on high spatial resolution predictions. Finally, a novel acceleration scheme was formulated and successfully tested, achieving reductions in computational resources of an order of magnitude.

46th AIAA Aerospace Sciences Meeting and Exhibit, 2008

16th Thermophysics Conference, 1981