How to accurately probe chemically reactive fiows with essential thermodynamic nonequilibrium effects is an open issue.Via the Chapman–Enskog analysis,the local nonequilibrium particle velocity distribution function ...How to accurately probe chemically reactive fiows with essential thermodynamic nonequilibrium effects is an open issue.Via the Chapman–Enskog analysis,the local nonequilibrium particle velocity distribution function is derived from the gas kinetic theory.It is demonstrated theoretically and numerically that the distribution function depends on the physical quantities and derivatives,and is independent of the chemical reactions directly as the chemical time scale is longer than the molecular relaxation time.Based on the simulation results of the discrete Boltzmann model,the departure between equilibrium and nonequilibrium distribution functions is obtained and analyzed around the detonation wave.In addition,it has been verified for the first time that the kinetic moments calculated by summations of the discrete distribution functions are close to those calculated by integrals of their original forms.展开更多
Kelvin–Helmholtz(KH)instability is a fundamental fluid instability that widely exists in nature and engineering.To better understand the dynamic process of the KH instability,the influence of the tangential velocity ...Kelvin–Helmholtz(KH)instability is a fundamental fluid instability that widely exists in nature and engineering.To better understand the dynamic process of the KH instability,the influence of the tangential velocity on the compressible KH instability is investigated by using the discrete Boltzmann method based on the nonequilibrium statistical physics.Both hydrodynamic and thermodynamic nonequilibrium(TNE)effects are probed and analyzed.It is found that,on the whole,the global density gradients,the TNE strength and area firstly increase and decrease afterwards.Both the global density gradient and heat flux intensity in the vertical direction are almost constant in the initial stage before a vortex forms.Moreover,with the increase of the tangential velocity,the KH instability evolves faster,hence the global density gradients,the TNE strength and area increase in the initial stage and achieve their peak earlier,and their maxima are higher for a larger tangential velocity.Physically,there are several competitive mechanisms in the evolution of the KH instability.(i)The physical gradients increase and the TNE effects are strengthened as the interface is elongated.The local physical gradients decrease and the local TNE intensity is weakened on account of the dissipation and/or diffusion.(ii)The global heat flux intensity is promoted when the physical gradients increase.As the contact area expands,the heat exchange is enhanced and the global heat flux intensity increases.(iii)The global TNE intensity reduces with the decreasing of physical gradients and increase with the increasing of TNE area.(iv)The nonequilibrium area increases as the fluid interface is elongated and is widened because of the dissipation and/or diffusion.展开更多
Kinetic effects in the inertial confinement fusion ignition process are far from clear.In this work,we study the Richtmyer-Meshkov instability and reshock processes by using a two-fluid discrete Boltzmann method.The w...Kinetic effects in the inertial confinement fusion ignition process are far from clear.In this work,we study the Richtmyer-Meshkov instability and reshock processes by using a two-fluid discrete Boltzmann method.The work begins by interpreting the experiment conducted by Collins and Jacobs(2002,J.Fluid Mech.464,113-136).It shows that the shock wave causes substances in close proximity to the substance interface to deviate more significantly from their thermodynamic equilibrium state.The thermodynamic non-equilibrium(TNE)quantities exhibit complex but inspiring kinetic effects in the shock process and behind the shock front.The kinetic effects are detected by two sets of TNE quantities.The first set includes∣Δ_(2)^(*)∣,∣Δ_(3,1)^(*),∣Δ_(3)^(*)∣,and∣Δ_(4,2)^(*)∣,which correspond to the intensities of the non-organized momentum Flux(NOMF),Non-Organized Energy Flux(NOEF),the flux of NOMF and the flux of NOEF.All four TNE measures abruptly increase in the shock process.The second set of TNE quantities includes■_(NOMF),■_(NOEF)and■_(sum),which denote the entropy production rates due to NOMF,NOEF and their summation,respectively.The mixing zone is the primary contributor to■_(NOEF),while the flow field region outside of the mixing zone is the primary contributor to■_(NOMF).Additionally,each substance exhibits different behaviors in terms of entropy production rate,and the lighter fluid has a higher entropy production rate than the heavier fluid.展开更多
To predict aeroheating performance of hypersonic vehicles accurately in thermochemical nonequilibrium flows accompanied by rarefaction effect,a Nonlinear Coupled Constitutive Relations(NCCR)model coupled with Gupta’s...To predict aeroheating performance of hypersonic vehicles accurately in thermochemical nonequilibrium flows accompanied by rarefaction effect,a Nonlinear Coupled Constitutive Relations(NCCR)model coupled with Gupta’s chemical models and Park’s two-temperature model is firstly proposed in this paper.Three typical cases are intensively investigated for further validation,including hypersonic flows over a two-dimensional cylinder,a RAM-C II flight vehicle and a type HTV-2 flight vehicle.The results predicted by NCCR solution,such as heat flux coefficient and electron number densities,are in better agreement with those of direct simulation Monte Carlo or flight data than Navier-Stokes equations,especially in the extremely nonequilibrium regions,which indicates the potential of the newly-developed solution to capture both thermochemical and rarefied nonequilibrium effects.The comparisons between the present solver and NCCR model without a two-temperature model are also conducted to demonstrate the significance of vibrational energy source term in the accurate simulation of high-Mach flows.展开更多
A multi-relaxation-time discrete Boltzmann model(DBM) with split collision is proposed for both subsonic and supersonic compressible reacting flows, where chemical reactions take place among various components. The ph...A multi-relaxation-time discrete Boltzmann model(DBM) with split collision is proposed for both subsonic and supersonic compressible reacting flows, where chemical reactions take place among various components. The physical model is based on a unified set of discrete Boltzmann equations that describes the evolution of each chemical species with adjustable acceleration, specific heat ratio, and Prandtl number. On the right-hand side of discrete Boltzmann equations, the collision,force, and reaction terms denote the change rates of distribution functions due to self-and crosscollisions, external forces, and chemical reactions, respectively. The source terms can be calculated in three ways, among which the matrix inversion method possesses the highest physical accuracy and computational efficiency. Through Chapman-Enskog analysis, it is proved that the DBM is consistent with the reactive Navier-Stokes equations, Fick's law and the Stefan-Maxwell diffusion equation in the hydrodynamic limit. Compared with the one-step-relaxation model, the split collision model offers a detailed and precise description of hydrodynamic, thermodynamic, and chemical nonequilibrium effects. Finally, the model is validated by six benchmarks, including multicomponent diffusion, mixture in the force field, Kelvin-Helmholtz instability, flame at constant pressure, opposing chemical reaction, and steady detonation.展开更多
Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenome...Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenomenological manner. It has been stated how the nonequilibrium effect should be observed in the spin-polarized quasiparticle tunneling currents, and pointed out that the detectable nonequilibrium effect could be found in the FIS tunneling junction at 77 K using HgBa2Ca2Cu3O8+? (Hg-1223) high-Tc superconductor rather than Bi2Sr2CaCu2O8+? (Bi-2212) one.展开更多
A discrete Boltzmann model(DBM) with symmetric velocity discretization is constructed for compressible systems with an adjustable specific heat ratio in the external force field. The proposed two-dimensional(2D) nine-...A discrete Boltzmann model(DBM) with symmetric velocity discretization is constructed for compressible systems with an adjustable specific heat ratio in the external force field. The proposed two-dimensional(2D) nine-velocity scheme has better spatial symmetry and numerical accuracy than the discretized velocity model in literature [Acta Aerodyn. Sin.40 98108(2022)] and owns higher computational efficiency than the one in literature [Phys. Rev. E 99 012142(2019)].In addition, the matrix inversion method is adopted to calculate the discrete equilibrium distribution function and force term, both of which satisfy nine independent kinetic moment relations. Moreover, the DBM could be used to study a few thermodynamic nonequilibrium effects beyond the Euler equations that are recovered from the kinetic model in the hydrodynamic limit via the Chapman–Enskog expansion. Finally, the present method is verified through typical numerical simulations, including the free-falling process, Sod’s shock tube, sound wave, compressible Rayleigh–Taylor instability,and translational motion of a 2D fluid system.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)under Grant Nos.51806116 and 11875001。
文摘How to accurately probe chemically reactive fiows with essential thermodynamic nonequilibrium effects is an open issue.Via the Chapman–Enskog analysis,the local nonequilibrium particle velocity distribution function is derived from the gas kinetic theory.It is demonstrated theoretically and numerically that the distribution function depends on the physical quantities and derivatives,and is independent of the chemical reactions directly as the chemical time scale is longer than the molecular relaxation time.Based on the simulation results of the discrete Boltzmann model,the departure between equilibrium and nonequilibrium distribution functions is obtained and analyzed around the detonation wave.In addition,it has been verified for the first time that the kinetic moments calculated by summations of the discrete distribution functions are close to those calculated by integrals of their original forms.
基金supported by the National Natural Science Foundation of China(Grant Nos.51806116 and 11875001)the Natural Science Foundation of Fujian Provinces(Grant Nos.2021J01652 and 2021J01655).
文摘Kelvin–Helmholtz(KH)instability is a fundamental fluid instability that widely exists in nature and engineering.To better understand the dynamic process of the KH instability,the influence of the tangential velocity on the compressible KH instability is investigated by using the discrete Boltzmann method based on the nonequilibrium statistical physics.Both hydrodynamic and thermodynamic nonequilibrium(TNE)effects are probed and analyzed.It is found that,on the whole,the global density gradients,the TNE strength and area firstly increase and decrease afterwards.Both the global density gradient and heat flux intensity in the vertical direction are almost constant in the initial stage before a vortex forms.Moreover,with the increase of the tangential velocity,the KH instability evolves faster,hence the global density gradients,the TNE strength and area increase in the initial stage and achieve their peak earlier,and their maxima are higher for a larger tangential velocity.Physically,there are several competitive mechanisms in the evolution of the KH instability.(i)The physical gradients increase and the TNE effects are strengthened as the interface is elongated.The local physical gradients decrease and the local TNE intensity is weakened on account of the dissipation and/or diffusion.(ii)The global heat flux intensity is promoted when the physical gradients increase.As the contact area expands,the heat exchange is enhanced and the global heat flux intensity increases.(iii)The global TNE intensity reduces with the decreasing of physical gradients and increase with the increasing of TNE area.(iv)The nonequilibrium area increases as the fluid interface is elongated and is widened because of the dissipation and/or diffusion.
基金supported by the National Natural Science Foundation of China(under Grant Nos.12172061,11875001,11575033,and 11975053)the opening project of the State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology)(under Grant No.KFJJ23-02M)+1 种基金Foundation of National Key Laboratory of Shock Wave and Detonation Physicsthe Foundation of National Key Laboratory of Computational Physics
文摘Kinetic effects in the inertial confinement fusion ignition process are far from clear.In this work,we study the Richtmyer-Meshkov instability and reshock processes by using a two-fluid discrete Boltzmann method.The work begins by interpreting the experiment conducted by Collins and Jacobs(2002,J.Fluid Mech.464,113-136).It shows that the shock wave causes substances in close proximity to the substance interface to deviate more significantly from their thermodynamic equilibrium state.The thermodynamic non-equilibrium(TNE)quantities exhibit complex but inspiring kinetic effects in the shock process and behind the shock front.The kinetic effects are detected by two sets of TNE quantities.The first set includes∣Δ_(2)^(*)∣,∣Δ_(3,1)^(*),∣Δ_(3)^(*)∣,and∣Δ_(4,2)^(*)∣,which correspond to the intensities of the non-organized momentum Flux(NOMF),Non-Organized Energy Flux(NOEF),the flux of NOMF and the flux of NOEF.All four TNE measures abruptly increase in the shock process.The second set of TNE quantities includes■_(NOMF),■_(NOEF)and■_(sum),which denote the entropy production rates due to NOMF,NOEF and their summation,respectively.The mixing zone is the primary contributor to■_(NOEF),while the flow field region outside of the mixing zone is the primary contributor to■_(NOMF).Additionally,each substance exhibits different behaviors in terms of entropy production rate,and the lighter fluid has a higher entropy production rate than the heavier fluid.
基金financially co-supported by the National Natural Science Foundation of China(Nos.12002306,U20B2007,11572284 and 6162790014)National Numerical Wind Tunnel Project,China(No.NNW2019ZT3-A08)。
文摘To predict aeroheating performance of hypersonic vehicles accurately in thermochemical nonequilibrium flows accompanied by rarefaction effect,a Nonlinear Coupled Constitutive Relations(NCCR)model coupled with Gupta’s chemical models and Park’s two-temperature model is firstly proposed in this paper.Three typical cases are intensively investigated for further validation,including hypersonic flows over a two-dimensional cylinder,a RAM-C II flight vehicle and a type HTV-2 flight vehicle.The results predicted by NCCR solution,such as heat flux coefficient and electron number densities,are in better agreement with those of direct simulation Monte Carlo or flight data than Navier-Stokes equations,especially in the extremely nonequilibrium regions,which indicates the potential of the newly-developed solution to capture both thermochemical and rarefied nonequilibrium effects.The comparisons between the present solver and NCCR model without a two-temperature model are also conducted to demonstrate the significance of vibrational energy source term in the accurate simulation of high-Mach flows.
基金supported by the National Natural Science Foundation of China(under Grant Nos. U2242214, 51806116 and 91441120)the Guangdong Basic and Applied Basic Research Foundation (under Grant Nos. 2022A1515012116and 2024A1515010927)+3 种基金the Natural Science Foundation of Fujian Province(under Grant Nos. 2021J01652, 2021J01655)the China Scholarship Council (No. 202306380288)partly supported by the Open Research Fund of Key Laboratory of Analytical Mathematics and Applications(Fujian Normal University),Ministry of Education,ChinaSupport from the UK Engineering and Physical Sciences Research Council under the project ‘UK Consortium on Mesoscale Engineering Sciences (UKCOMES)’(Grant No. EP/X035875/1) is gratefully acknowledged。
文摘A multi-relaxation-time discrete Boltzmann model(DBM) with split collision is proposed for both subsonic and supersonic compressible reacting flows, where chemical reactions take place among various components. The physical model is based on a unified set of discrete Boltzmann equations that describes the evolution of each chemical species with adjustable acceleration, specific heat ratio, and Prandtl number. On the right-hand side of discrete Boltzmann equations, the collision,force, and reaction terms denote the change rates of distribution functions due to self-and crosscollisions, external forces, and chemical reactions, respectively. The source terms can be calculated in three ways, among which the matrix inversion method possesses the highest physical accuracy and computational efficiency. Through Chapman-Enskog analysis, it is proved that the DBM is consistent with the reactive Navier-Stokes equations, Fick's law and the Stefan-Maxwell diffusion equation in the hydrodynamic limit. Compared with the one-step-relaxation model, the split collision model offers a detailed and precise description of hydrodynamic, thermodynamic, and chemical nonequilibrium effects. Finally, the model is validated by six benchmarks, including multicomponent diffusion, mixture in the force field, Kelvin-Helmholtz instability, flame at constant pressure, opposing chemical reaction, and steady detonation.
文摘Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenomenological manner. It has been stated how the nonequilibrium effect should be observed in the spin-polarized quasiparticle tunneling currents, and pointed out that the detectable nonequilibrium effect could be found in the FIS tunneling junction at 77 K using HgBa2Ca2Cu3O8+? (Hg-1223) high-Tc superconductor rather than Bi2Sr2CaCu2O8+? (Bi-2212) one.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51806116, U2242214, and 11875329)Guangdong Basic and Applied Basic Research Foundation (Grant No. 2022A1515012116)the Natural Science Foundation of Fujian Province, China (Grant Nos. 2021J01652 and 2021J01655)。
文摘A discrete Boltzmann model(DBM) with symmetric velocity discretization is constructed for compressible systems with an adjustable specific heat ratio in the external force field. The proposed two-dimensional(2D) nine-velocity scheme has better spatial symmetry and numerical accuracy than the discretized velocity model in literature [Acta Aerodyn. Sin.40 98108(2022)] and owns higher computational efficiency than the one in literature [Phys. Rev. E 99 012142(2019)].In addition, the matrix inversion method is adopted to calculate the discrete equilibrium distribution function and force term, both of which satisfy nine independent kinetic moment relations. Moreover, the DBM could be used to study a few thermodynamic nonequilibrium effects beyond the Euler equations that are recovered from the kinetic model in the hydrodynamic limit via the Chapman–Enskog expansion. Finally, the present method is verified through typical numerical simulations, including the free-falling process, Sod’s shock tube, sound wave, compressible Rayleigh–Taylor instability,and translational motion of a 2D fluid system.
