The Experts below are selected from a list of 10758 Experts worldwide ranked by ideXlab platform
Surendra N. Tiwari - One of the best experts on this subject based on the ideXlab platform.
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Investigation of three-dimensional separation at wing/body junctions in supersonic Flows
Journal of Aircraft, 1994Co-Authors: Balakrishnan Lakshmanan, Surendra N. TiwariAbstract:The problem of three-dimensional separation at a wing/body junction has been investigated numerically using a three-dimensional Navier-Stokes code which employs the MacCormack's time split, finite volume technique. An algebraic grid generation technique is used for generating the grid at a wing/body junction. Specific computational results on velocity and pressure distribution in the Separated Flow Region are compared with the experimental results. A parametric study of Flow parameters, such as Mach and Reynolds numbers, have been carried out to understand their effect in interaction Flowfield. The parametric study indicates dependency of the number of vortices at the junction on Mach number and Reynolds number.
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Investigation of three-dimensional separation at wing/body junctions in supersonic Flows using TVD MacCormack's scheme
31st Aerospace Sciences Meeting, 1993Co-Authors: Balakrishnan Lakshmanan, Surendra N. TiwariAbstract:A Total Variation Diminishing (TVD) MacCormack scheme is used to study the three-dimensional separation at wing/body junctions in supersonic Flows. The new scheme is robust, resolves discontinuities well with-out any numerical oscillations present in the Flow field. Moreover, this new scheme does not contain any problem dependent parameters to be adjusted and many production codes employing MacCormack algorithm can be easily updated to good effect. Numerical simulation carried out in laminar supersonic junction Flows using the new scheme yields improved prediction for the separation location and the axial velocity profiles in the Separated Flow Region.
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Comparative Study of MacCormack and TVD MacCormack Schemes for Three-Dimensional Separation at Wing/Body Junctions in Supersonic Flows
SAE Technical Paper Series, 1992Co-Authors: Balakrishnan Lakshmanan, Surendra N. TiwariAbstract:A robust, discontinuity-resolving TVD MacCormack scheme containing no dependent parameters requiring adjustment is presently used to investigate the 3D separation of wing/body junction Flows at supersonic speeds. Many production codes employing MacCormack schemes can be adapted to use this method. A numerical simulation of laminar supersonic junction Flow is found to yield improved separation location predictions, as well as the axial velocity profiles in the Separated Flow Region.
Richard T. Schoephoerster - One of the best experts on this subject based on the ideXlab platform.
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Vortex Shedding in Steady Flow Through a Model of an Arterial Stenosis and Its Relevance to Mural Platelet Deposition
Annals of Biomedical Engineering, 1999Co-Authors: Danny Bluestein, Carlos Gutierrez, Mateo Londono, Richard T. SchoephoersterAbstract:In this study, the development of unsteady vortical formations in the Separated Flow Region distal to a stenosis throat is presented and compared with the platelet deposition measurements, to enhance our understanding of the mechanisms involved in platelet kinetics in Flowing blood. Qualitative and quantitative Flow visualization and numerical simulations were performed in a model of a streamlined axisymmetric stenosis with an area reduction of 84% at the throat of the stenosis. Measurements were performed at Reynolds numbers (Re), based on upstream diameter and average velocity, ranging from 300 to 1800. Both the digital particle image visualization method employed and the numerical simulations were able to capture the motion of the vortices through the Separated Flow Region. Periodic shedding of vortices began at approximately Re=375 and continued for the full range of Re studied. The locales at which these vortices are initiated, their size, and their life span, were a function of Re. The numerical simulations of turbulent Flow through the stenosis model entailed a detailed depiction of the process of vortex shedding in the Separated Flow Region downstream of the stenosis. These Flow patterns were used to elucidate the mechanisms involved in blood platelet kinetics and deposition in the area in and around an arterial stenosis. The unsteady Flow development in the recirculation Region is hypothesized as the mechanism for observed changes in the distribution of mural platelet deposition between Re=300, 900, and 1800, despite only a marginal variation in the size and shape of the recirculation zone under these Flow conditions. © 1999 Biomedical Engineering Society. PAC99: 8719Uv, 8710+e
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Vortex shedding in steady Flow through a model of an arterial stenosis and its relevance to mural platelet deposition.
Annals of Biomedical Engineering, 1999Co-Authors: Danny Bluestein, Carlos Gutierrez, Mateo Londono, Richard T. SchoephoersterAbstract:In this study, the development of unsteady vortical formations in the Separated Flow Region distal to a stenosis throat is presented and compared with the platelet deposition measurements, to enhance our understanding of the mecha- nisms involved in platelet kinetics in Flowing blood. Qualitative and quantitative Flow visualization and numerical simulations were performed in a model of a streamlined axisymmetric stenosis with an area reduction of 84% at the throat of the stenosis. Measurements were performed at Reynolds numbers ~Re!, based on upstream diameter and average velocity, ranging from 300 to 1800. Both the digital particle image visualization method employed and the numerical simulations were able to capture the motion of the vortices through the Separated Flow Region. Periodic shedding of vortices began at approximately Re5375 and continued for the full range of Re studied. The locales at which these vortices are initiated, their size, and their life span, were a function of Re. The numerical simulations of turbulent Flow through the stenosis model entailed a detailed depiction of the process of vortex shedding in the Separated Flow Region downstream of the stenosis. These Flow patterns were used to elucidate the mechanisms involved in blood plate- let kinetics and deposition in the area in and around an arterial stenosis. The unsteady Flow development in the recirculation Region is hypothesized as the mechanism for observed changes in the distribution of mural platelet deposition between Re 5300, 900, and 1800, despite only a marginal variation in the size and shape of the recirculation zone under these Flow con- ditions. © 1999 Biomedical Engineering Society. @S0090-6964~99!00306-9#
Balakrishnan Lakshmanan - One of the best experts on this subject based on the ideXlab platform.
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Investigation of three-dimensional separation at wing/body junctions in supersonic Flows
Journal of Aircraft, 1994Co-Authors: Balakrishnan Lakshmanan, Surendra N. TiwariAbstract:The problem of three-dimensional separation at a wing/body junction has been investigated numerically using a three-dimensional Navier-Stokes code which employs the MacCormack's time split, finite volume technique. An algebraic grid generation technique is used for generating the grid at a wing/body junction. Specific computational results on velocity and pressure distribution in the Separated Flow Region are compared with the experimental results. A parametric study of Flow parameters, such as Mach and Reynolds numbers, have been carried out to understand their effect in interaction Flowfield. The parametric study indicates dependency of the number of vortices at the junction on Mach number and Reynolds number.
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Investigation of three-dimensional separation at wing/body junctions in supersonic Flows using TVD MacCormack's scheme
31st Aerospace Sciences Meeting, 1993Co-Authors: Balakrishnan Lakshmanan, Surendra N. TiwariAbstract:A Total Variation Diminishing (TVD) MacCormack scheme is used to study the three-dimensional separation at wing/body junctions in supersonic Flows. The new scheme is robust, resolves discontinuities well with-out any numerical oscillations present in the Flow field. Moreover, this new scheme does not contain any problem dependent parameters to be adjusted and many production codes employing MacCormack algorithm can be easily updated to good effect. Numerical simulation carried out in laminar supersonic junction Flows using the new scheme yields improved prediction for the separation location and the axial velocity profiles in the Separated Flow Region.
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Comparative Study of MacCormack and TVD MacCormack Schemes for Three-Dimensional Separation at Wing/Body Junctions in Supersonic Flows
SAE Technical Paper Series, 1992Co-Authors: Balakrishnan Lakshmanan, Surendra N. TiwariAbstract:A robust, discontinuity-resolving TVD MacCormack scheme containing no dependent parameters requiring adjustment is presently used to investigate the 3D separation of wing/body junction Flows at supersonic speeds. Many production codes employing MacCormack schemes can be adapted to use this method. A numerical simulation of laminar supersonic junction Flow is found to yield improved separation location predictions, as well as the axial velocity profiles in the Separated Flow Region.
Danny Bluestein - One of the best experts on this subject based on the ideXlab platform.
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Vortex Shedding in Steady Flow Through a Model of an Arterial Stenosis and Its Relevance to Mural Platelet Deposition
Annals of Biomedical Engineering, 1999Co-Authors: Danny Bluestein, Carlos Gutierrez, Mateo Londono, Richard T. SchoephoersterAbstract:In this study, the development of unsteady vortical formations in the Separated Flow Region distal to a stenosis throat is presented and compared with the platelet deposition measurements, to enhance our understanding of the mechanisms involved in platelet kinetics in Flowing blood. Qualitative and quantitative Flow visualization and numerical simulations were performed in a model of a streamlined axisymmetric stenosis with an area reduction of 84% at the throat of the stenosis. Measurements were performed at Reynolds numbers (Re), based on upstream diameter and average velocity, ranging from 300 to 1800. Both the digital particle image visualization method employed and the numerical simulations were able to capture the motion of the vortices through the Separated Flow Region. Periodic shedding of vortices began at approximately Re=375 and continued for the full range of Re studied. The locales at which these vortices are initiated, their size, and their life span, were a function of Re. The numerical simulations of turbulent Flow through the stenosis model entailed a detailed depiction of the process of vortex shedding in the Separated Flow Region downstream of the stenosis. These Flow patterns were used to elucidate the mechanisms involved in blood platelet kinetics and deposition in the area in and around an arterial stenosis. The unsteady Flow development in the recirculation Region is hypothesized as the mechanism for observed changes in the distribution of mural platelet deposition between Re=300, 900, and 1800, despite only a marginal variation in the size and shape of the recirculation zone under these Flow conditions. © 1999 Biomedical Engineering Society. PAC99: 8719Uv, 8710+e
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Vortex shedding in steady Flow through a model of an arterial stenosis and its relevance to mural platelet deposition.
Annals of Biomedical Engineering, 1999Co-Authors: Danny Bluestein, Carlos Gutierrez, Mateo Londono, Richard T. SchoephoersterAbstract:In this study, the development of unsteady vortical formations in the Separated Flow Region distal to a stenosis throat is presented and compared with the platelet deposition measurements, to enhance our understanding of the mecha- nisms involved in platelet kinetics in Flowing blood. Qualitative and quantitative Flow visualization and numerical simulations were performed in a model of a streamlined axisymmetric stenosis with an area reduction of 84% at the throat of the stenosis. Measurements were performed at Reynolds numbers ~Re!, based on upstream diameter and average velocity, ranging from 300 to 1800. Both the digital particle image visualization method employed and the numerical simulations were able to capture the motion of the vortices through the Separated Flow Region. Periodic shedding of vortices began at approximately Re5375 and continued for the full range of Re studied. The locales at which these vortices are initiated, their size, and their life span, were a function of Re. The numerical simulations of turbulent Flow through the stenosis model entailed a detailed depiction of the process of vortex shedding in the Separated Flow Region downstream of the stenosis. These Flow patterns were used to elucidate the mechanisms involved in blood plate- let kinetics and deposition in the area in and around an arterial stenosis. The unsteady Flow development in the recirculation Region is hypothesized as the mechanism for observed changes in the distribution of mural platelet deposition between Re 5300, 900, and 1800, despite only a marginal variation in the size and shape of the recirculation zone under these Flow con- ditions. © 1999 Biomedical Engineering Society. @S0090-6964~99!00306-9#
Hiromasa Kato - One of the best experts on this subject based on the ideXlab platform.
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New forward/backward sweeping parabolized Navier-Stokes algorithm
Journal of Spacecraft and Rockets, 2003Co-Authors: Hiromasa Kato, John C. TannehillAbstract:A new forward/backward sweeping parabolized Navier-Stokes algorithm has been developed to compute efficiently supersonic/hypersonic Flowfields with embedded Separated Regions. The algorithm splits the streamwise flux vector using the Steger-Warming method and employs multiple forward/backward sweeps of the Flowfield to duplicate the results that would be obtained with the complete Navier-Stokes equations. The forward/backward sweeping of the Flowfield significantly reduces the number of iterations required over previous iterative parabolized Navier-Stokes algorithms. Once a Separated Flow Region is computed, the algorithm returns to the usual forward-space-marching mode until the next Separated Flow Region is encountered. The algorithm has been successfully incorporated into NASA's parabolized Navier-Stokes UPS code. The new algorithm has been applied to three Separated Flow test cases consisting of Flow over a compression ramp and two Flows over a hollow-cylinder-flare geometry. The present numerical results are in excellent agreement with complete Navier-Stokes computations and experimental data.
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A new forward-backward sweeping parabolized Navier-Stokes algorithm with application to magnetohydrodynamic Flows
1Co-Authors: Hiromasa KatoAbstract:A new forward-backward sweeping parabolized Navier-Stokes algorithm has been developed to efficiently compute supersonic/hypersonic Flowfields with embedded Separated Regions. The algorithm splits the streamwise flux vector using the Steger-Warming method and employs multiple forward/backward sweeps of the Flowfield in order to duplicate the results that would be obtained with the complete Navier-Stokes equations. The forward/backward sweeping of the Flowfield significantly reduces the number of iterations required over previous iterative parabolized Navier-Stokes algorithms. Once a Separated Flow Region is computed, the algorithm returns to the usual forward-space-marching mode until the next Separated Flow Region is encountered. The new algorithm has been applied to three Separated Flow test cases consisting of Flow over a compression ramp and two Flows over a hollow-cylinder-flare geometry. The present numerical results are in excellent agreement with complete Navier-Stokes computations and experimental data. In addition, the new algorithm has been extended to efficiently compute magnetohydrodynamic (MHD) Flows in the low magnetic Reynolds number regime. In this regime, the electrical conductivity is low and the induced magnetic field is negligible compared to the applied magnetic field. This allows the MHD effects to be modeled by introducing source terms into the governing equations. Turbulence has been included by modifying the Baldwin-Lomax turbulence model to account for MHD effects. The new algorithm with MHD effects included has been used to compute both laminar and turbulent, supersonic, MHD Flows over flat plates, and 3-D supersonic viscous Flows in an experimental MHD channel. The new algorithms have been successfully incorporated into NASA's parabolized Navier-Stokes (UPS) code.
