Understanding interactions between gas molecules and solid surface is key to the aerodynamic design of high-speed,high-altitude aerospace vehicles,but there is a large dispersion of gas-surface interaction parameters ...Understanding interactions between gas molecules and solid surface is key to the aerodynamic design of high-speed,high-altitude aerospace vehicles,but there is a large dispersion of gas-surface interaction parameters or namely accommodation coefficients.The uncertainty results partly from different considerations of the interaction between gas molecules in various experimental and numerical methods.In this study,effects of gas-gas molecules interaction are systematically discussed by comparing two different approaches of molecular dynamics simulation of high-speed argon molecules scattering on a graphite surface.The popularly-used“single scattering”approach repeats the scattering process of a single gas molecule without considering the gas-gas molecules interaction.The newly-developed“continual scattering”approach continually shoots gas molecules at the surface,considering collisions between gas molecules in addition to gas molecules’collisions with surface.Gas-surface interaction features in the two approaches are compared and discussed under various affecting factors including rarefaction degree,gas-surface interaction strength,surface temperature and incident velocity.It is shown that these two approaches usually produce different accommodation coefficients,and the corresponding mechanisms are explained.This study could help clarify some doubts about the selection of accommodation coefficients in engineering practice,and also provide an instruction on design of an appropriate molecular dynamics simulation approach.展开更多
The accurate prediction for aerodynamic drag of spacecraft in very low Earth orbit(VLEO) is a fundamental prerequisite for aerospace missions in VLEO. The present work calculates aerodynamic drag of the Gravity Field ...The accurate prediction for aerodynamic drag of spacecraft in very low Earth orbit(VLEO) is a fundamental prerequisite for aerospace missions in VLEO. The present work calculates aerodynamic drag of the Gravity Field and Steady-State Ocean Circulation Explorer(GOCE) satellite using the test particle Monte Carlo(TPMC) method. The primary goal is to obtain a comprehensive understanding of surface pressure and skin friction on the spacecraft surface and assess the sensitivity of aerodynamic drag to the gas-surface interaction(GSI) models. Results indicate that surface pressure is mainly distributed on the front of the satellite body and panels while skin friction is primarily distributed on the sides. In addition, as the GSI model changes from diffuse to specular reflection, the total drag coefficient is reduced at operation altitudes above 170 km. Therefore, the satellite surface should be processed so carefully that the GSI remains far from diffuse reflection from the view point of the drag-reduce design.展开更多
Flows of a rarefied gas between coaxial circular cylinders with nonuniform surface properties are studied on the basis of kinetic theory. It is assumed that the outer cylinder is a diffuse reflection boundary and the ...Flows of a rarefied gas between coaxial circular cylinders with nonuniform surface properties are studied on the basis of kinetic theory. It is assumed that the outer cylinder is a diffuse reflection boundary and the inner cylinder is a Maxwell-type boundary whose accommodation coefficient varies in the circumferential direction. Three fundamental flows are studied: 1) a flow caused by the rotation of the outer cylinder (Couette flow), 2) a flow induced between the cylinders at rest kept at different temperatures (heat transfer problem), and 3) a flow induced by the circumferential temperature distribution along the cylindrical surfaces (thermal creep flow). The linearized ES-BGK model of the Boltzmann equation is numerically analyzed using a finite difference method. The time-independent behavior of the gas is studied over a wide range of the gas rarefaction degree, the radii ratio, and a parameter characterizing the distribution of the accommodation coefficient. Due to an effect of nonuniform surface properties, a local heat transfer occurs between the gas and the cylindrical surfaces in Couette flow;a local tangential stress arises in the heat transfer problem. However, the total heat transfer between the two cylinders in Couette flow and the total torque acting on the inner cylinder in the heat transfer problem vanish irrespective of the flow parameters. Two nondegenerate reciprocity relations arise due to the effect of nonuniform surface properties. The reciprocity relations among the above-mentioned three flows are numerically confirmed over a wide range of the flow parameters. The force on the inner cylinder, which also arises due to the effect of nonuniform surface properties in Couette flow and the heat transfer problems, is studied.展开更多
Collisions are of fundamental importance in many relevant physico-chemical phenomena in the gas phase and at the gas-surface interface.Collision-induced energy transfer not only offers a sensitive probe of interatomic...Collisions are of fundamental importance in many relevant physico-chemical phenomena in the gas phase and at the gas-surface interface.Collision-induced energy transfer not only offers a sensitive probe of interatomic interactions,but also impacts an array of processes ranging from transport to reactivity.This perspective highlights some recent advances on collision-induced energy transfer dynamics.In the gas phase,cold collisions revealed remarkable quantum effects and stereodynamics of bimolecular inelastic scattering,which motivated development of new state-to-state quantum scattering methods.For surface processes,experiments of hydrogen atom scattering from various surfaces combined with first-principles molecular dynamics simulations shed valuable light on the relative importance of adiabatic energy transfer to surface phonons and nonadiabatic energy transfer to surface electrons.We outline further challenges in these fields and expect more fruitful interplay between experiment and theory.展开更多
A dynamical Lie algebraic method has been applied to treating the quantum dynamics of dissociative adsorption of H2 on a static flat metal surface. An LEPS potential energy surface has been used to describe the intera...A dynamical Lie algebraic method has been applied to treating the quantum dynamics of dissociative adsorption of H2 on a static flat metal surface. An LEPS potential energy surface has been used to describe the interaction of H2 with Ni(100) surface. The dependence of the initial state-selected dissociation probability was obtained analytically on the initial kinetic energy and time. A comparison with other theoretical calculations and experiments is made. The results show that the method can be effectively used to describe the dynamics of reactive gas-surface scattering.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.12072343).
文摘Understanding interactions between gas molecules and solid surface is key to the aerodynamic design of high-speed,high-altitude aerospace vehicles,but there is a large dispersion of gas-surface interaction parameters or namely accommodation coefficients.The uncertainty results partly from different considerations of the interaction between gas molecules in various experimental and numerical methods.In this study,effects of gas-gas molecules interaction are systematically discussed by comparing two different approaches of molecular dynamics simulation of high-speed argon molecules scattering on a graphite surface.The popularly-used“single scattering”approach repeats the scattering process of a single gas molecule without considering the gas-gas molecules interaction.The newly-developed“continual scattering”approach continually shoots gas molecules at the surface,considering collisions between gas molecules in addition to gas molecules’collisions with surface.Gas-surface interaction features in the two approaches are compared and discussed under various affecting factors including rarefaction degree,gas-surface interaction strength,surface temperature and incident velocity.It is shown that these two approaches usually produce different accommodation coefficients,and the corresponding mechanisms are explained.This study could help clarify some doubts about the selection of accommodation coefficients in engineering practice,and also provide an instruction on design of an appropriate molecular dynamics simulation approach.
文摘The accurate prediction for aerodynamic drag of spacecraft in very low Earth orbit(VLEO) is a fundamental prerequisite for aerospace missions in VLEO. The present work calculates aerodynamic drag of the Gravity Field and Steady-State Ocean Circulation Explorer(GOCE) satellite using the test particle Monte Carlo(TPMC) method. The primary goal is to obtain a comprehensive understanding of surface pressure and skin friction on the spacecraft surface and assess the sensitivity of aerodynamic drag to the gas-surface interaction(GSI) models. Results indicate that surface pressure is mainly distributed on the front of the satellite body and panels while skin friction is primarily distributed on the sides. In addition, as the GSI model changes from diffuse to specular reflection, the total drag coefficient is reduced at operation altitudes above 170 km. Therefore, the satellite surface should be processed so carefully that the GSI remains far from diffuse reflection from the view point of the drag-reduce design.
文摘Flows of a rarefied gas between coaxial circular cylinders with nonuniform surface properties are studied on the basis of kinetic theory. It is assumed that the outer cylinder is a diffuse reflection boundary and the inner cylinder is a Maxwell-type boundary whose accommodation coefficient varies in the circumferential direction. Three fundamental flows are studied: 1) a flow caused by the rotation of the outer cylinder (Couette flow), 2) a flow induced between the cylinders at rest kept at different temperatures (heat transfer problem), and 3) a flow induced by the circumferential temperature distribution along the cylindrical surfaces (thermal creep flow). The linearized ES-BGK model of the Boltzmann equation is numerically analyzed using a finite difference method. The time-independent behavior of the gas is studied over a wide range of the gas rarefaction degree, the radii ratio, and a parameter characterizing the distribution of the accommodation coefficient. Due to an effect of nonuniform surface properties, a local heat transfer occurs between the gas and the cylindrical surfaces in Couette flow;a local tangential stress arises in the heat transfer problem. However, the total heat transfer between the two cylinders in Couette flow and the total torque acting on the inner cylinder in the heat transfer problem vanish irrespective of the flow parameters. Two nondegenerate reciprocity relations arise due to the effect of nonuniform surface properties. The reciprocity relations among the above-mentioned three flows are numerically confirmed over a wide range of the flow parameters. The force on the inner cylinder, which also arises due to the effect of nonuniform surface properties in Couette flow and the heat transfer problems, is studied.
基金supported by the National Natural Science Foundation of China(22241302 and 22233003 to D.X.and 22325304 and 22073089 to B.J.)the National Science Foundation(CHE-1951328 and CHE-2306975 to H.G.)+1 种基金the Department of Energy(DE-SC0015997 to H.G.)the CAS。
文摘Collisions are of fundamental importance in many relevant physico-chemical phenomena in the gas phase and at the gas-surface interface.Collision-induced energy transfer not only offers a sensitive probe of interatomic interactions,but also impacts an array of processes ranging from transport to reactivity.This perspective highlights some recent advances on collision-induced energy transfer dynamics.In the gas phase,cold collisions revealed remarkable quantum effects and stereodynamics of bimolecular inelastic scattering,which motivated development of new state-to-state quantum scattering methods.For surface processes,experiments of hydrogen atom scattering from various surfaces combined with first-principles molecular dynamics simulations shed valuable light on the relative importance of adiabatic energy transfer to surface phonons and nonadiabatic energy transfer to surface electrons.We outline further challenges in these fields and expect more fruitful interplay between experiment and theory.
基金Project supported by the National Natural Science Foundation of China (Grant No. 19694033)partially by the State Key Laboratory of Theoretical and Computational Chemistry of Jilin University (Grant No. 9801).
文摘A dynamical Lie algebraic method has been applied to treating the quantum dynamics of dissociative adsorption of H2 on a static flat metal surface. An LEPS potential energy surface has been used to describe the interaction of H2 with Ni(100) surface. The dependence of the initial state-selected dissociation probability was obtained analytically on the initial kinetic energy and time. A comparison with other theoretical calculations and experiments is made. The results show that the method can be effectively used to describe the dynamics of reactive gas-surface scattering.
