Nonequilibrium kinetics effects in Richtmyer–Meshkov instability and reshock processes

Abstract

Kinetic effects in the inertial confinement fusion ignition process are far from clear. In this work, we study the Richtmyer-Meshkov instability (RMI) and reshock processes by using a two-fluid discrete Boltzmann method (DBM). The work begins from interpreting the experiment conducted by Collins and Jacobs [J. Fluid Mech. 464,113-136(2002)]. 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 NonEquilibrium (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 │Δ2 *│,│Δ3,1 *│,│Δ3 *│,and │Δ4,2 *│, 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 SNOMF, SNOEF and Ssum. The mixing zone is the primary contributor to SNOEF, while the flow field region outside of the mixing zone is the primary contributor to SNOMF. 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.


Influence of Density Ratios on Richtmyer–Meshkov Instability with Non-Equilibrium Effects in the Reshock Process

“…In particular, numerical simulation has promoted relative research due to its convenience and efficiency, and it can enrich our understanding of the RM instability from multiple perspectives. These perspectives are mainly attributed to the following three levels: macroscopic [18][19][20][21][22][23][24], microscopic [25,26], and mesoscopic aspects [27][28][29]. In the macroscopic view, various codes based on hydrodynamic governing equations, such as Euler or Navier-Stokes equations, have been widely used to simulate fluid instability.…”

“…In 2018, Chen et al [28] used the multiple-relaxation-time DBM to investigate the non-equilibrium characteristics of a coexistence system involving both RM and Rayleigh-Taylor instability and found that the non-equilibrium effect of the system increases as the Mach number increases, while the effect of gravity acceleration on the non-equilibrium characteristics is different at various phases. In 2023, Shan et al [29] employed the two-fluid DBM to investigate the non-equilibrium kinetic effects on the RM instability and reshock process and found that lighter fluid has a higher entropy production rate than heavier fluid. Moreover, the DBM also provides new insights for complex fluid systems, such as hydrodynamic instability [39][40][41][42][43], multiphase flow [44,45], reactive flow [46], etc.…”