Harry Dwyer - Academia.edu (original) (raw)

Papers by Harry Dwyer

Research paper thumbnail of AIAA 3rd Computational Fluid Dynamics Conference : a collection of technical papers, Albuquerque, N. MEX, June 27-28, 1977

Research paper thumbnail of A collection of technical papers : AIAA 6th Computational Fluid Dynamics Conference, July 13-15, 1983, Danvers, Massachusetts

American Institute of Aeronautics and Astronautics eBooks, 1983

Research paper thumbnail of Computational Fluid Dynamics Within Bifurcated Abdominal Aortic Stent-Grafts

Journal of Endovascular Therapy, Apr 1, 2007

To assess the hemodynamic forces on a bifurcated abdominal aortic stent-graft under realistic con... more To assess the hemodynamic forces on a bifurcated abdominal aortic stent-graft under realistic conditions of flow, blood pressure, and sac pressure. Methods: Computational fluid dynamics was used to study the temporal and spatial variations in surface pressure and shear through the cardiac cycle on models of bifurcated stent-grafts derived from computed tomography in 4 patients who had previously undergone endovascular repair of abdominal aortic aneurysm (AAA). The trunk, bifurcation, and limbs of the graft were analyzed separately and as parts of a unified whole. Analyses were repeated under varying conditions of sac pressure, reflecting different conditions of perigraft flow and sac diameter change. Results: Pressure-related forces were far larger than flow-related forces in all 3 segments of all 4 cases. The largest forces acted at the bifurcation of the stent-graft. High sac pressures, seen in patients with endoleak or aneurysm dilatation, were associated with reduced transmural pressure and low-pressure-derived forces. Conclusion: Several parameters of stent-graft design affect the magnitude and distribution of forces on a bifurcated stent-graft. The forces on a stent-graft are also affected by the pressure within the aneurysm sac, which depends on stent-graft performance.

Research paper thumbnail of Reply to the Comments by J. R. Brock

Research paper thumbnail of A collection of technical papers : AIAA 6th Computational Fluid Dynamics Conference, July 13-15, 1983, Danvers, Massachusetts

Research paper thumbnail of Aerodynamic forces and heat transfer for 3-D flow over a sphere in a pipe

33rd Aerospace Sciences Meeting and Exhibit, 1995

Research paper thumbnail of Shape optimization for aerodynamic efficiency and low observability

23rd Fluid Dynamics, Plasmadynamics, and Lasers Conference, 1993

Field methods based on the finite-difference approximations of the time-domain Maxwell's equa... more Field methods based on the finite-difference approximations of the time-domain Maxwell's equations and the potential-flow equation have been developed to solve the multidisciplinary problem of airfoil shaping for aerodynamic efficiency and low radar cross section (RCS). A parametric study and an optimization study employing the two analysis methods are presented to illustrate their combined capabilities. The parametric study shows that for frontal radar illumination, the RCS of an airfoil is independent of the chordwise location of maximum thickness but depends strongly on the maximum thickness, leading-edge radius, and leadingedge shape. In addition, this study shows that the RCS of an airfoil can be reduced without significant effects on its transonic aerodynamic efficiency by reducing the leading-edge radius and/or modifying the shape of the leading edge. The optimization study involves the minimization of wave drag for a non-lifting, symmetrical airfoil with constraints on the airfoil maximum thickness and monostatic RCS. This optimization study shows that the two analysis methods can be used effectively to design aerodynamically efficient airfoils with certain desired RCS characteristics.

Research paper thumbnail of Evaluation of potential for refrigerant recovery from decommissioned shipping containers at California ports

This paper describes progressive energy efficiency improvements made to refrigeration systems and... more This paper describes progressive energy efficiency improvements made to refrigeration systems and components used in the container refrigeration application. A systems approach and implementation of new component designs for compressors, heat exchangers, and air moving systems have allowed cooling and heating to be accomplished while reducing energy consumption. Compressor improvements include enhancements to reciprocating piston designs and more recently, adoption of scroll compressor technologies. Heat exchangers include heat transfer surfaces with highly efficient, enhanced profiles to maximize heat transfer. Air management systems include improved fan geometries and ducting designs. In addition, current components are now leveraging new technologies in materials and designs to improve sustainability. The use of natural refrigerant (CO2) and low GWP foams as well as the elimination of hazardous materials are examples of recent steps being taken to

Research paper thumbnail of Development of a Retrofit Fuel Cell Auxiliary Power Unit for Truck Idle Reduction

SAE Technical Paper Series, 2004

Résumé/Abstract In the last five years, there have been multiple demonstrations of fuel cell auxi... more Résumé/Abstract In the last five years, there have been multiple demonstrations of fuel cell auxiliary power units (APUs) which provide power in lieu of idling of the main vehicle engine. The Institute of Transportation Studies at the University of California Davis has ...

Research paper thumbnail of Time accurate solutions of the Navier-Stokes equations for reacting flows

Tenth International Conference on Numerical Methods in Fluid Dynamics

The major conclusions of the investigations are the following: 1. A significant improvement in t... more The major conclusions of the investigations are the following: 1. A significant improvement in the numerical simulation of gas phase combustion processes at low Mach number has been achieved with the use of a pressure correction type method. The transport equations have been solved with a predictor/corrector algorithm of the ADI type. 2. The use of a direct banded solver for the Poisson equation for the pressure correction algorithm considerably improves the efficiency and accuracy of the method. 3. The pressure correction method is a time consistent approximation to the momentum equations which effectively decouples the velocity change between time steps into a vortical and potential component.

Research paper thumbnail of The influence of freestream vorticity on particle lift, drag, and heat transfer

27th Aerospace Sciences Meeting, 1989

ABSTRACT Numerical solutions have been obtained for steady, linear shear flow past a heated spher... more ABSTRACT Numerical solutions have been obtained for steady, linear shear flow past a heated spherical particle for a wide range of Reynolds numbers and shear rates. The three-dimensional solutions for velocity, pressure and temperature calculated in this work will be the basis for future correlations for drag, lift, and heat transfer rate. The particle was kept at a fixed temperature different from the far-field temperature. It was found that although the dimensionless heat transfer (that is, the Nusselt number) increased with increasing Reynolds number for fixed shear rate, the rate of heat transfer was insensitive to changes in shear rate for fixed values of the Reynolds number.

Research paper thumbnail of Some influences of particle shape on drag and heat transfer

Physics of Fluids A: Fluid Dynamics, 1990

ABSTRACT A comprehensive study of the three-dimensional flow of intermediate Re over an ellipsoid... more ABSTRACT A comprehensive study of the three-dimensional flow of intermediate Re over an ellipsoid of revolution was carried out using a finite volume numerical method. Flowfields solutions show that the total skin friction drag and the total heat transfer correlate well with the particle surface area and are independent of particle orientation. For three-dimensional flows, the maximum in heat flux and total shear stress occurs at a different spatial location than the previous stagnation point in the flow. The maximum in the heat flux and the total shear stress usually occurs near the major axis of the body. The finite volume formulation of the transport equations appears to be a good framework for solving complex problems involving droplet mass transfer and deformation.

Research paper thumbnail of ACCESS Magazine Fall 2001

Research paper thumbnail of A dynamic combustion model of a decomposing and reacting monopropellant

26th Aerospace Sciences Meeting, 1988

The purpose of this research study is to calculate the dynamic behavior of a decomposing and reac... more The purpose of this research study is to calculate the dynamic behavior of a decomposing and reacting monopropellant with the characteristics of the popular HAN and TEAN like materials currently being widely studied for high pressure applications. The present research investigation has successfully solved the NavierStokes equations in a timedependent and onedimensional form for a chemical model of the monopropellant. The numerical solution was based on the finite volume formulation of the basic equations, and employed the use of adaptive griding methods to resolve the extremely thin flame zones that developed. The basic method of solution was found to be very efficient and accurately reproduced some previous results for premixed hydrogen flame propagation. The monopropellant results showed that the adaptive griding methods resolved the physical and chemical processes completely, and it has been determined that the HAN decomposition reaction is the rate determining step for the system. It has also been determined that convective effects are large, and could play a role in system performance. Introduction An unsteady model of the high pressure decomposition and burning 'bf a monopropellant has been developed and applied parametrically to different compositions and geometries. The solution of the model equations has been obtained numerically and use has been made of adaptive griding methods to follow both the motion of the monopropellant interface and the unsteady temperature gradients in the reacting products. The description of the monopropellant burning process has been simplified in the present study, however variable transport and thermodynamic properties have been employed, as well as Arrhenius kinetics with widely different activation energies. At the present time it is very difficult to formulate a model of monopropellant burning because of the extreme conditions of the high pressure and high temperature surroundings and the complex chemistry associated with the materials utilized. It is the purpose of the present investigation to develop a very general numerical model which can be utilized as a diagnostic tool to parametrically study experimental systems. In many practical monopropellant systems these model equations will have to be solved over a wide range of pressures and chemical compositions in order to understand experiments that have been carried out on the burning of monopropellants in burners and in droplet form. It is hoped from these studies that the correct physics and chemistry can be narrowed down from the many propositions currently being iormulated. * This research was partially supported by Sandia National Laboratories, Livermore, California v Present Model The basic starting point for the investigation has been the equations of mass, energy and species transport in moving control volume form (The time dependent velocity was determined from the continuity equation and density from the equation of state). The transport equations in this form allow for the introduction of moving interfaces and the application of moving grids with adaptive methods in a clear and simple fashion. The basic equations are W Control Volume Equations

Research paper thumbnail of Modeling Stationary Power for Heavy-Duty Trucks: Engine Idling vs. Fuel Cell APUs

SAE Technical Paper Series, 2004

Abstract: Line-haul truck engines are frequently idled to power hotel loads (ie heating, air cond... more Abstract: Line-haul truck engines are frequently idled to power hotel loads (ie heating, air conditioning, and lighting) during rest periods. Comfortable cabin climate conditions are required in order for mandatory driver rests periods to effectively enhance safety; however, ...

Research paper thumbnail of Development of a Retrofit Fuel Cell Auxiliary Power Unit for Truck Idle Reduction

SAE Technical Paper Series, 2004

Résumé/Abstract In the last five years, there have been multiple demonstrations of fuel cell auxi... more Résumé/Abstract In the last five years, there have been multiple demonstrations of fuel cell auxiliary power units (APUs) which provide power in lieu of idling of the main vehicle engine. The Institute of Transportation Studies at the University of California Davis has ...

Research paper thumbnail of The influence of freestream vorticity on particle lift, drag, and heat transfer

27th Aerospace Sciences Meeting, 1989

ABSTRACT Numerical solutions have been obtained for steady, linear shear flow past a heated spher... more ABSTRACT Numerical solutions have been obtained for steady, linear shear flow past a heated spherical particle for a wide range of Reynolds numbers and shear rates. The three-dimensional solutions for velocity, pressure and temperature calculated in this work will be the basis for future correlations for drag, lift, and heat transfer rate. The particle was kept at a fixed temperature different from the far-field temperature. It was found that although the dimensionless heat transfer (that is, the Nusselt number) increased with increasing Reynolds number for fixed shear rate, the rate of heat transfer was insensitive to changes in shear rate for fixed values of the Reynolds number.

Research paper thumbnail of Magnus forces on spinning supersonic cones. II - Inviscid flow

AIAA Journal, 1976

The numerical solution of steady, three-dimensional, inviscid, supersonic flows is applied to the... more The numerical solution of steady, three-dimensional, inviscid, supersonic flows is applied to the calculation of Magnus forces on spinning cones at angle of attack. The Magnus force is made up of several contributions. The contribution of the asymmetrical boundary-layer displacement-thickness interaction with the inviscid flowfield is considered here. Three-dimensional, laminar boundary-layer solutions for the spinning cone were obtained by methods described in Part I of this paper. The displacement-thickness contribution to the Magnus force is calculated by solving the complete inviscid flowfield over body shapes obtained by adding the three-dimensional displacement thickness to the cone radius. The gasdynamic equations are solved by applying MacCormack's second-order shock-capturing finite-difference technique. Special precautions had to be taken, in both finitedifferencing and in applying the surface boundary conditions, to maintain enough significant digits in the pressure calculation, since the Magnus force is as small as one part in 300 of the normal force for some cases considered. The displacement-thickness contribution to the Magnus force, along with three other contributions described in Part I of this paper, are summarized here in Part II. The considerable cancellation effect observed among the four contributions shows that all of the components must be included if accurate predictions of the Magnus force are to be obtained.

Research paper thumbnail of A dynamic combustion model of a decomposing and reacting monopropellant

26th Aerospace Sciences Meeting, 1988

The purpose of this research study is to calculate the dynamic behavior of a decomposing and reac... more The purpose of this research study is to calculate the dynamic behavior of a decomposing and reacting monopropellant with the characteristics of the popular HAN and TEAN like materials currently being widely studied for high pressure applications. The present research investigation has successfully solved the NavierStokes equations in a timedependent and onedimensional form for a chemical model of the monopropellant. The numerical solution was based on the finite volume formulation of the basic equations, and employed the use of adaptive griding methods to resolve the extremely thin flame zones that developed. The basic method of solution was found to be very efficient and accurately reproduced some previous results for premixed hydrogen flame propagation. The monopropellant results showed that the adaptive griding methods resolved the physical and chemical processes completely, and it has been determined that the HAN decomposition reaction is the rate determining step for the system. It has also been determined that convective effects are large, and could play a role in system performance. Introduction An unsteady model of the high pressure decomposition and burning 'bf a monopropellant has been developed and applied parametrically to different compositions and geometries. The solution of the model equations has been obtained numerically and use has been made of adaptive griding methods to follow both the motion of the monopropellant interface and the unsteady temperature gradients in the reacting products. The description of the monopropellant burning process has been simplified in the present study, however variable transport and thermodynamic properties have been employed, as well as Arrhenius kinetics with widely different activation energies. At the present time it is very difficult to formulate a model of monopropellant burning because of the extreme conditions of the high pressure and high temperature surroundings and the complex chemistry associated with the materials utilized. It is the purpose of the present investigation to develop a very general numerical model which can be utilized as a diagnostic tool to parametrically study experimental systems. In many practical monopropellant systems these model equations will have to be solved over a wide range of pressures and chemical compositions in order to understand experiments that have been carried out on the burning of monopropellants in burners and in droplet form. It is hoped from these studies that the correct physics and chemistry can be narrowed down from the many propositions currently being iormulated. * This research was partially supported by Sandia National Laboratories, Livermore, California v Present Model The basic starting point for the investigation has been the equations of mass, energy and species transport in moving control volume form (The time dependent velocity was determined from the continuity equation and density from the equation of state). The transport equations in this form allow for the introduction of moving interfaces and the application of moving grids with adaptive methods in a clear and simple fashion. The basic equations are W Control Volume Equations

Research paper thumbnail of Magnus forces on spinning supersonic cones. II - Inviscid flow

AIAA Journal, 1976

The numerical solution of steady, three-dimensional, inviscid, supersonic flows is applied to the... more The numerical solution of steady, three-dimensional, inviscid, supersonic flows is applied to the calculation of Magnus forces on spinning cones at angle of attack. The Magnus force is made up of several contributions. The contribution of the asymmetrical boundary-layer displacement-thickness interaction with the inviscid flowfield is considered here. Three-dimensional, laminar boundary-layer solutions for the spinning cone were obtained by methods described in Part I of this paper. The displacement-thickness contribution to the Magnus force is calculated by solving the complete inviscid flowfield over body shapes obtained by adding the three-dimensional displacement thickness to the cone radius. The gasdynamic equations are solved by applying MacCormack's second-order shock-capturing finite-difference technique. Special precautions had to be taken, in both finitedifferencing and in applying the surface boundary conditions, to maintain enough significant digits in the pressure calculation, since the Magnus force is as small as one part in 300 of the normal force for some cases considered. The displacement-thickness contribution to the Magnus force, along with three other contributions described in Part I of this paper, are summarized here in Part II. The considerable cancellation effect observed among the four contributions shows that all of the components must be included if accurate predictions of the Magnus force are to be obtained.

Research paper thumbnail of AIAA 3rd Computational Fluid Dynamics Conference : a collection of technical papers, Albuquerque, N. MEX, June 27-28, 1977

Research paper thumbnail of A collection of technical papers : AIAA 6th Computational Fluid Dynamics Conference, July 13-15, 1983, Danvers, Massachusetts

American Institute of Aeronautics and Astronautics eBooks, 1983

Research paper thumbnail of Computational Fluid Dynamics Within Bifurcated Abdominal Aortic Stent-Grafts

Journal of Endovascular Therapy, Apr 1, 2007

To assess the hemodynamic forces on a bifurcated abdominal aortic stent-graft under realistic con... more To assess the hemodynamic forces on a bifurcated abdominal aortic stent-graft under realistic conditions of flow, blood pressure, and sac pressure. Methods: Computational fluid dynamics was used to study the temporal and spatial variations in surface pressure and shear through the cardiac cycle on models of bifurcated stent-grafts derived from computed tomography in 4 patients who had previously undergone endovascular repair of abdominal aortic aneurysm (AAA). The trunk, bifurcation, and limbs of the graft were analyzed separately and as parts of a unified whole. Analyses were repeated under varying conditions of sac pressure, reflecting different conditions of perigraft flow and sac diameter change. Results: Pressure-related forces were far larger than flow-related forces in all 3 segments of all 4 cases. The largest forces acted at the bifurcation of the stent-graft. High sac pressures, seen in patients with endoleak or aneurysm dilatation, were associated with reduced transmural pressure and low-pressure-derived forces. Conclusion: Several parameters of stent-graft design affect the magnitude and distribution of forces on a bifurcated stent-graft. The forces on a stent-graft are also affected by the pressure within the aneurysm sac, which depends on stent-graft performance.

Research paper thumbnail of Reply to the Comments by J. R. Brock

Research paper thumbnail of A collection of technical papers : AIAA 6th Computational Fluid Dynamics Conference, July 13-15, 1983, Danvers, Massachusetts

Research paper thumbnail of Aerodynamic forces and heat transfer for 3-D flow over a sphere in a pipe

33rd Aerospace Sciences Meeting and Exhibit, 1995

Research paper thumbnail of Shape optimization for aerodynamic efficiency and low observability

23rd Fluid Dynamics, Plasmadynamics, and Lasers Conference, 1993

Field methods based on the finite-difference approximations of the time-domain Maxwell's equa... more Field methods based on the finite-difference approximations of the time-domain Maxwell's equations and the potential-flow equation have been developed to solve the multidisciplinary problem of airfoil shaping for aerodynamic efficiency and low radar cross section (RCS). A parametric study and an optimization study employing the two analysis methods are presented to illustrate their combined capabilities. The parametric study shows that for frontal radar illumination, the RCS of an airfoil is independent of the chordwise location of maximum thickness but depends strongly on the maximum thickness, leading-edge radius, and leadingedge shape. In addition, this study shows that the RCS of an airfoil can be reduced without significant effects on its transonic aerodynamic efficiency by reducing the leading-edge radius and/or modifying the shape of the leading edge. The optimization study involves the minimization of wave drag for a non-lifting, symmetrical airfoil with constraints on the airfoil maximum thickness and monostatic RCS. This optimization study shows that the two analysis methods can be used effectively to design aerodynamically efficient airfoils with certain desired RCS characteristics.

Research paper thumbnail of Evaluation of potential for refrigerant recovery from decommissioned shipping containers at California ports

This paper describes progressive energy efficiency improvements made to refrigeration systems and... more This paper describes progressive energy efficiency improvements made to refrigeration systems and components used in the container refrigeration application. A systems approach and implementation of new component designs for compressors, heat exchangers, and air moving systems have allowed cooling and heating to be accomplished while reducing energy consumption. Compressor improvements include enhancements to reciprocating piston designs and more recently, adoption of scroll compressor technologies. Heat exchangers include heat transfer surfaces with highly efficient, enhanced profiles to maximize heat transfer. Air management systems include improved fan geometries and ducting designs. In addition, current components are now leveraging new technologies in materials and designs to improve sustainability. The use of natural refrigerant (CO2) and low GWP foams as well as the elimination of hazardous materials are examples of recent steps being taken to

Research paper thumbnail of Development of a Retrofit Fuel Cell Auxiliary Power Unit for Truck Idle Reduction

SAE Technical Paper Series, 2004

Résumé/Abstract In the last five years, there have been multiple demonstrations of fuel cell auxi... more Résumé/Abstract In the last five years, there have been multiple demonstrations of fuel cell auxiliary power units (APUs) which provide power in lieu of idling of the main vehicle engine. The Institute of Transportation Studies at the University of California Davis has ...

Research paper thumbnail of Time accurate solutions of the Navier-Stokes equations for reacting flows

Tenth International Conference on Numerical Methods in Fluid Dynamics

The major conclusions of the investigations are the following: 1. A significant improvement in t... more The major conclusions of the investigations are the following: 1. A significant improvement in the numerical simulation of gas phase combustion processes at low Mach number has been achieved with the use of a pressure correction type method. The transport equations have been solved with a predictor/corrector algorithm of the ADI type. 2. The use of a direct banded solver for the Poisson equation for the pressure correction algorithm considerably improves the efficiency and accuracy of the method. 3. The pressure correction method is a time consistent approximation to the momentum equations which effectively decouples the velocity change between time steps into a vortical and potential component.

Research paper thumbnail of The influence of freestream vorticity on particle lift, drag, and heat transfer

27th Aerospace Sciences Meeting, 1989

ABSTRACT Numerical solutions have been obtained for steady, linear shear flow past a heated spher... more ABSTRACT Numerical solutions have been obtained for steady, linear shear flow past a heated spherical particle for a wide range of Reynolds numbers and shear rates. The three-dimensional solutions for velocity, pressure and temperature calculated in this work will be the basis for future correlations for drag, lift, and heat transfer rate. The particle was kept at a fixed temperature different from the far-field temperature. It was found that although the dimensionless heat transfer (that is, the Nusselt number) increased with increasing Reynolds number for fixed shear rate, the rate of heat transfer was insensitive to changes in shear rate for fixed values of the Reynolds number.

Research paper thumbnail of Some influences of particle shape on drag and heat transfer

Physics of Fluids A: Fluid Dynamics, 1990

ABSTRACT A comprehensive study of the three-dimensional flow of intermediate Re over an ellipsoid... more ABSTRACT A comprehensive study of the three-dimensional flow of intermediate Re over an ellipsoid of revolution was carried out using a finite volume numerical method. Flowfields solutions show that the total skin friction drag and the total heat transfer correlate well with the particle surface area and are independent of particle orientation. For three-dimensional flows, the maximum in heat flux and total shear stress occurs at a different spatial location than the previous stagnation point in the flow. The maximum in the heat flux and the total shear stress usually occurs near the major axis of the body. The finite volume formulation of the transport equations appears to be a good framework for solving complex problems involving droplet mass transfer and deformation.

Research paper thumbnail of ACCESS Magazine Fall 2001

Research paper thumbnail of A dynamic combustion model of a decomposing and reacting monopropellant

26th Aerospace Sciences Meeting, 1988

The purpose of this research study is to calculate the dynamic behavior of a decomposing and reac... more The purpose of this research study is to calculate the dynamic behavior of a decomposing and reacting monopropellant with the characteristics of the popular HAN and TEAN like materials currently being widely studied for high pressure applications. The present research investigation has successfully solved the NavierStokes equations in a timedependent and onedimensional form for a chemical model of the monopropellant. The numerical solution was based on the finite volume formulation of the basic equations, and employed the use of adaptive griding methods to resolve the extremely thin flame zones that developed. The basic method of solution was found to be very efficient and accurately reproduced some previous results for premixed hydrogen flame propagation. The monopropellant results showed that the adaptive griding methods resolved the physical and chemical processes completely, and it has been determined that the HAN decomposition reaction is the rate determining step for the system. It has also been determined that convective effects are large, and could play a role in system performance. Introduction An unsteady model of the high pressure decomposition and burning 'bf a monopropellant has been developed and applied parametrically to different compositions and geometries. The solution of the model equations has been obtained numerically and use has been made of adaptive griding methods to follow both the motion of the monopropellant interface and the unsteady temperature gradients in the reacting products. The description of the monopropellant burning process has been simplified in the present study, however variable transport and thermodynamic properties have been employed, as well as Arrhenius kinetics with widely different activation energies. At the present time it is very difficult to formulate a model of monopropellant burning because of the extreme conditions of the high pressure and high temperature surroundings and the complex chemistry associated with the materials utilized. It is the purpose of the present investigation to develop a very general numerical model which can be utilized as a diagnostic tool to parametrically study experimental systems. In many practical monopropellant systems these model equations will have to be solved over a wide range of pressures and chemical compositions in order to understand experiments that have been carried out on the burning of monopropellants in burners and in droplet form. It is hoped from these studies that the correct physics and chemistry can be narrowed down from the many propositions currently being iormulated. * This research was partially supported by Sandia National Laboratories, Livermore, California v Present Model The basic starting point for the investigation has been the equations of mass, energy and species transport in moving control volume form (The time dependent velocity was determined from the continuity equation and density from the equation of state). The transport equations in this form allow for the introduction of moving interfaces and the application of moving grids with adaptive methods in a clear and simple fashion. The basic equations are W Control Volume Equations

Research paper thumbnail of Modeling Stationary Power for Heavy-Duty Trucks: Engine Idling vs. Fuel Cell APUs

SAE Technical Paper Series, 2004

Abstract: Line-haul truck engines are frequently idled to power hotel loads (ie heating, air cond... more Abstract: Line-haul truck engines are frequently idled to power hotel loads (ie heating, air conditioning, and lighting) during rest periods. Comfortable cabin climate conditions are required in order for mandatory driver rests periods to effectively enhance safety; however, ...

Research paper thumbnail of Development of a Retrofit Fuel Cell Auxiliary Power Unit for Truck Idle Reduction

SAE Technical Paper Series, 2004

Résumé/Abstract In the last five years, there have been multiple demonstrations of fuel cell auxi... more Résumé/Abstract In the last five years, there have been multiple demonstrations of fuel cell auxiliary power units (APUs) which provide power in lieu of idling of the main vehicle engine. The Institute of Transportation Studies at the University of California Davis has ...

Research paper thumbnail of The influence of freestream vorticity on particle lift, drag, and heat transfer

27th Aerospace Sciences Meeting, 1989

ABSTRACT Numerical solutions have been obtained for steady, linear shear flow past a heated spher... more ABSTRACT Numerical solutions have been obtained for steady, linear shear flow past a heated spherical particle for a wide range of Reynolds numbers and shear rates. The three-dimensional solutions for velocity, pressure and temperature calculated in this work will be the basis for future correlations for drag, lift, and heat transfer rate. The particle was kept at a fixed temperature different from the far-field temperature. It was found that although the dimensionless heat transfer (that is, the Nusselt number) increased with increasing Reynolds number for fixed shear rate, the rate of heat transfer was insensitive to changes in shear rate for fixed values of the Reynolds number.

Research paper thumbnail of Magnus forces on spinning supersonic cones. II - Inviscid flow

AIAA Journal, 1976

The numerical solution of steady, three-dimensional, inviscid, supersonic flows is applied to the... more The numerical solution of steady, three-dimensional, inviscid, supersonic flows is applied to the calculation of Magnus forces on spinning cones at angle of attack. The Magnus force is made up of several contributions. The contribution of the asymmetrical boundary-layer displacement-thickness interaction with the inviscid flowfield is considered here. Three-dimensional, laminar boundary-layer solutions for the spinning cone were obtained by methods described in Part I of this paper. The displacement-thickness contribution to the Magnus force is calculated by solving the complete inviscid flowfield over body shapes obtained by adding the three-dimensional displacement thickness to the cone radius. The gasdynamic equations are solved by applying MacCormack's second-order shock-capturing finite-difference technique. Special precautions had to be taken, in both finitedifferencing and in applying the surface boundary conditions, to maintain enough significant digits in the pressure calculation, since the Magnus force is as small as one part in 300 of the normal force for some cases considered. The displacement-thickness contribution to the Magnus force, along with three other contributions described in Part I of this paper, are summarized here in Part II. The considerable cancellation effect observed among the four contributions shows that all of the components must be included if accurate predictions of the Magnus force are to be obtained.

Research paper thumbnail of A dynamic combustion model of a decomposing and reacting monopropellant

26th Aerospace Sciences Meeting, 1988

The purpose of this research study is to calculate the dynamic behavior of a decomposing and reac... more The purpose of this research study is to calculate the dynamic behavior of a decomposing and reacting monopropellant with the characteristics of the popular HAN and TEAN like materials currently being widely studied for high pressure applications. The present research investigation has successfully solved the NavierStokes equations in a timedependent and onedimensional form for a chemical model of the monopropellant. The numerical solution was based on the finite volume formulation of the basic equations, and employed the use of adaptive griding methods to resolve the extremely thin flame zones that developed. The basic method of solution was found to be very efficient and accurately reproduced some previous results for premixed hydrogen flame propagation. The monopropellant results showed that the adaptive griding methods resolved the physical and chemical processes completely, and it has been determined that the HAN decomposition reaction is the rate determining step for the system. It has also been determined that convective effects are large, and could play a role in system performance. Introduction An unsteady model of the high pressure decomposition and burning 'bf a monopropellant has been developed and applied parametrically to different compositions and geometries. The solution of the model equations has been obtained numerically and use has been made of adaptive griding methods to follow both the motion of the monopropellant interface and the unsteady temperature gradients in the reacting products. The description of the monopropellant burning process has been simplified in the present study, however variable transport and thermodynamic properties have been employed, as well as Arrhenius kinetics with widely different activation energies. At the present time it is very difficult to formulate a model of monopropellant burning because of the extreme conditions of the high pressure and high temperature surroundings and the complex chemistry associated with the materials utilized. It is the purpose of the present investigation to develop a very general numerical model which can be utilized as a diagnostic tool to parametrically study experimental systems. In many practical monopropellant systems these model equations will have to be solved over a wide range of pressures and chemical compositions in order to understand experiments that have been carried out on the burning of monopropellants in burners and in droplet form. It is hoped from these studies that the correct physics and chemistry can be narrowed down from the many propositions currently being iormulated. * This research was partially supported by Sandia National Laboratories, Livermore, California v Present Model The basic starting point for the investigation has been the equations of mass, energy and species transport in moving control volume form (The time dependent velocity was determined from the continuity equation and density from the equation of state). The transport equations in this form allow for the introduction of moving interfaces and the application of moving grids with adaptive methods in a clear and simple fashion. The basic equations are W Control Volume Equations

Research paper thumbnail of Magnus forces on spinning supersonic cones. II - Inviscid flow

AIAA Journal, 1976

The numerical solution of steady, three-dimensional, inviscid, supersonic flows is applied to the... more The numerical solution of steady, three-dimensional, inviscid, supersonic flows is applied to the calculation of Magnus forces on spinning cones at angle of attack. The Magnus force is made up of several contributions. The contribution of the asymmetrical boundary-layer displacement-thickness interaction with the inviscid flowfield is considered here. Three-dimensional, laminar boundary-layer solutions for the spinning cone were obtained by methods described in Part I of this paper. The displacement-thickness contribution to the Magnus force is calculated by solving the complete inviscid flowfield over body shapes obtained by adding the three-dimensional displacement thickness to the cone radius. The gasdynamic equations are solved by applying MacCormack's second-order shock-capturing finite-difference technique. Special precautions had to be taken, in both finitedifferencing and in applying the surface boundary conditions, to maintain enough significant digits in the pressure calculation, since the Magnus force is as small as one part in 300 of the normal force for some cases considered. The displacement-thickness contribution to the Magnus force, along with three other contributions described in Part I of this paper, are summarized here in Part II. The considerable cancellation effect observed among the four contributions shows that all of the components must be included if accurate predictions of the Magnus force are to be obtained.