The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform

Patrick Jenny - One of the best experts on this subject based on the ideXlab platform.

  • a fokker planck based kinetic model for diatomic rarefied gas flows
    Physics of Fluids, 2013
    Co-Authors: Hossein Miladi Gorji, Patrick Jenny
    Abstract:

    A Fokker–Planck based kinetic model is presented here, which also accounts for internal energy modes characteristic for diatomic gas Molecules. The model is based on a Fokker–Planck approximation of the Boltzmann equation for Monatomic Molecules, whereas phenomenological principles were employed for the derivation. It is shown that the model honors the equipartition theorem in equilibrium and fulfills the Landau–Teller relaxation equations for internal degrees of freedom. The objective behind this approximate kinetic model is accuracy at reasonably low computational cost. This can be achieved due to the fact that the resulting stochastic differential equations are continuous in time; therefore, no collisions between the simulated particles have to be calculated. Besides, because of the devised energy conserving time integration scheme, it is not required to resolve the collisional scales, i.e., the mean collision time and the mean free path of Molecules. This, of course, gives rise to much more efficient ...

  • A Fokker–Planck based kinetic model for diatomic rarefied gas flows
    Physics of Fluids, 2013
    Co-Authors: M. Hossein Gorji, Patrick Jenny
    Abstract:

    A Fokker–Planck based kinetic model is presented here, which also accounts for internal energy modes characteristic for diatomic gas Molecules. The model is based on a Fokker–Planck approximation of the Boltzmann equation for Monatomic Molecules, whereas phenomenological principles were employed for the derivation. It is shown that the model honors the equipartition theorem in equilibrium and fulfills the Landau–Teller relaxation equations for internal degrees of freedom. The objective behind this approximate kinetic model is accuracy at reasonably low computational cost. This can be achieved due to the fact that the resulting stochastic differential equations are continuous in time; therefore, no collisions between the simulated particles have to be calculated. Besides, because of the devised energy conserving time integration scheme, it is not required to resolve the collisional scales, i.e., the mean collision time and the mean free path of Molecules. This, of course, gives rise to much more efficient simulations with respect to other particle methods, especially the conventional direct simulation Monte Carlo (DSMC), for small and moderate Knudsen numbers. To examine the new approach, first the computational cost of the model was compared with respect to DSMC, where significant speed up could be obtained for small Knudsen numbers. Second, the structure of a high Mach shock (in nitrogen) was studied, and the good performance of the model for such out of equilibrium conditions could be demonstrated. At last, a hypersonic flow of nitrogen over a wedge was studied, where good agreement with respect to DSMC (with level to level transition model) for vibrational and translational temperatures is shown.

Hossein Miladi Gorji - One of the best experts on this subject based on the ideXlab platform.

  • a fokker planck based kinetic model for diatomic rarefied gas flows
    Physics of Fluids, 2013
    Co-Authors: Hossein Miladi Gorji, Patrick Jenny
    Abstract:

    A Fokker–Planck based kinetic model is presented here, which also accounts for internal energy modes characteristic for diatomic gas Molecules. The model is based on a Fokker–Planck approximation of the Boltzmann equation for Monatomic Molecules, whereas phenomenological principles were employed for the derivation. It is shown that the model honors the equipartition theorem in equilibrium and fulfills the Landau–Teller relaxation equations for internal degrees of freedom. The objective behind this approximate kinetic model is accuracy at reasonably low computational cost. This can be achieved due to the fact that the resulting stochastic differential equations are continuous in time; therefore, no collisions between the simulated particles have to be calculated. Besides, because of the devised energy conserving time integration scheme, it is not required to resolve the collisional scales, i.e., the mean collision time and the mean free path of Molecules. This, of course, gives rise to much more efficient ...

M. Hossein Gorji - One of the best experts on this subject based on the ideXlab platform.

  • A Fokker–Planck based kinetic model for diatomic rarefied gas flows
    Physics of Fluids, 2013
    Co-Authors: M. Hossein Gorji, Patrick Jenny
    Abstract:

    A Fokker–Planck based kinetic model is presented here, which also accounts for internal energy modes characteristic for diatomic gas Molecules. The model is based on a Fokker–Planck approximation of the Boltzmann equation for Monatomic Molecules, whereas phenomenological principles were employed for the derivation. It is shown that the model honors the equipartition theorem in equilibrium and fulfills the Landau–Teller relaxation equations for internal degrees of freedom. The objective behind this approximate kinetic model is accuracy at reasonably low computational cost. This can be achieved due to the fact that the resulting stochastic differential equations are continuous in time; therefore, no collisions between the simulated particles have to be calculated. Besides, because of the devised energy conserving time integration scheme, it is not required to resolve the collisional scales, i.e., the mean collision time and the mean free path of Molecules. This, of course, gives rise to much more efficient simulations with respect to other particle methods, especially the conventional direct simulation Monte Carlo (DSMC), for small and moderate Knudsen numbers. To examine the new approach, first the computational cost of the model was compared with respect to DSMC, where significant speed up could be obtained for small Knudsen numbers. Second, the structure of a high Mach shock (in nitrogen) was studied, and the good performance of the model for such out of equilibrium conditions could be demonstrated. At last, a hypersonic flow of nitrogen over a wedge was studied, where good agreement with respect to DSMC (with level to level transition model) for vibrational and translational temperatures is shown.

Masahiko Shibahara - One of the best experts on this subject based on the ideXlab platform.

  • Local mass and energy transports in evaporation processes from a vapor-liquid interface in a slit pore based on molecular dynamics
    AIP Advances, 2018
    Co-Authors: Kohei Fujiwara, Masahiko Shibahara
    Abstract:

    Molecular evaporation processes from a vapor-liquid interface formed in a slit-like pore were examined based on the classical molecular dynamics method, in order to elucidate a molecular mechanism of local mass and energy transports in a slit. The calculation system consisted of Monatomic Molecules and atoms which interact through the 12-6 Lennard-Jones potential. At first, a liquid was situated in a slit with a vapor-liquid interface, and instantaneous amounts of the mass and energy fluxes defined locally in the slit were obtained in two dimensions to reveal local fluctuation properties of the fluid in equilibrium states. Then, imposing a temperature gradient in the calculation system, non-equilibrium evaporation processes in the slit were investigated in details based on the local mass and energy fluxes. In this study, we focused on the fluid which is in the vicinity of the solid surface and in contact with the vapor phase. In the non-equilibrium evaporation processes, the results revealed that the loca...

  • Local mass and energy transports in evaporation processes from a vapor-liquid interface in a slit pore based on molecular dynamics
    AIP Publishing LLC, 2018
    Co-Authors: Kohei Fujiwara, Masahiko Shibahara
    Abstract:

    Molecular evaporation processes from a vapor-liquid interface formed in a slit-like pore were examined based on the classical molecular dynamics method, in order to elucidate a molecular mechanism of local mass and energy transports in a slit. The calculation system consisted of Monatomic Molecules and atoms which interact through the 12-6 Lennard-Jones potential. At first, a liquid was situated in a slit with a vapor-liquid interface, and instantaneous amounts of the mass and energy fluxes defined locally in the slit were obtained in two dimensions to reveal local fluctuation properties of the fluid in equilibrium states. Then, imposing a temperature gradient in the calculation system, non-equilibrium evaporation processes in the slit were investigated in details based on the local mass and energy fluxes. In this study, we focused on the fluid which is in the vicinity of the solid surface and in contact with the vapor phase. In the non-equilibrium evaporation processes, the results revealed that the local energy transport mechanism in the vicinity of the solid surface is different from that of the vapor phase, especially in the case of the relatively strong fluid-solid interaction. The results also revealed that the local mass transport in the vicinity of the solid surface can be interpreted based on the mechanism of the local energy transport, and the mechanism provides valuable information about pictures of the evaporation phenomena especially in the vicinity of the hydrophilic surfaces. It suggests that evaluating and changing this mechanism of the local energy transport are necessary to control the local mass flux more precisely in the vicinity of the solid surface

Kohei Fujiwara - One of the best experts on this subject based on the ideXlab platform.

  • Local mass and energy transports in evaporation processes from a vapor-liquid interface in a slit pore based on molecular dynamics
    AIP Advances, 2018
    Co-Authors: Kohei Fujiwara, Masahiko Shibahara
    Abstract:

    Molecular evaporation processes from a vapor-liquid interface formed in a slit-like pore were examined based on the classical molecular dynamics method, in order to elucidate a molecular mechanism of local mass and energy transports in a slit. The calculation system consisted of Monatomic Molecules and atoms which interact through the 12-6 Lennard-Jones potential. At first, a liquid was situated in a slit with a vapor-liquid interface, and instantaneous amounts of the mass and energy fluxes defined locally in the slit were obtained in two dimensions to reveal local fluctuation properties of the fluid in equilibrium states. Then, imposing a temperature gradient in the calculation system, non-equilibrium evaporation processes in the slit were investigated in details based on the local mass and energy fluxes. In this study, we focused on the fluid which is in the vicinity of the solid surface and in contact with the vapor phase. In the non-equilibrium evaporation processes, the results revealed that the loca...

  • Local mass and energy transports in evaporation processes from a vapor-liquid interface in a slit pore based on molecular dynamics
    AIP Publishing LLC, 2018
    Co-Authors: Kohei Fujiwara, Masahiko Shibahara
    Abstract:

    Molecular evaporation processes from a vapor-liquid interface formed in a slit-like pore were examined based on the classical molecular dynamics method, in order to elucidate a molecular mechanism of local mass and energy transports in a slit. The calculation system consisted of Monatomic Molecules and atoms which interact through the 12-6 Lennard-Jones potential. At first, a liquid was situated in a slit with a vapor-liquid interface, and instantaneous amounts of the mass and energy fluxes defined locally in the slit were obtained in two dimensions to reveal local fluctuation properties of the fluid in equilibrium states. Then, imposing a temperature gradient in the calculation system, non-equilibrium evaporation processes in the slit were investigated in details based on the local mass and energy fluxes. In this study, we focused on the fluid which is in the vicinity of the solid surface and in contact with the vapor phase. In the non-equilibrium evaporation processes, the results revealed that the local energy transport mechanism in the vicinity of the solid surface is different from that of the vapor phase, especially in the case of the relatively strong fluid-solid interaction. The results also revealed that the local mass transport in the vicinity of the solid surface can be interpreted based on the mechanism of the local energy transport, and the mechanism provides valuable information about pictures of the evaporation phenomena especially in the vicinity of the hydrophilic surfaces. It suggests that evaluating and changing this mechanism of the local energy transport are necessary to control the local mass flux more precisely in the vicinity of the solid surface