Collaboration and competition between Richtmyer-Meshkov instability and Rayleigh-Taylor instability

The two-dimensional Richtmyer-Meshkov Instability (RMI) system and the coexisting system combined with Rayleigh-Taylor Instability (RTI) are simulated with a multiple-relaxation time discrete Boltzmann model. In the RMI system, the non-equilibrium characteristics are compared with those of the RTI system, and some similarities and differences are obtained: In these two types of instability systems, heat conduction plays a major role in the degree of correlation; the correlation between thermodynamic non-equilibrium strength and nonuniformity of density in RMI is still relatively high, but the magnitude of gradual reduction over time is much greater than that of the RTI; the correlation degree curves of the RTI system are relatively smooth, but in the RMI system, there are many abrupt changes due to the existence and development of the shock wave. In the coexisting system combined with RTI, first, from the macroperspective (interface disturbance amplitude, amplitude growth rate, interface reversal mechanism, etc.), the collaboration and competition mechanisms of the two instabilities are investigated. The parameter regions in which RMI and RTI dominate are given. Second, the effects of the gravity acceleration and Mach number on non-equilibrium are carefully studied. By affecting the amplitude growth and the density gradient, the gravity acceleration has different effects on the non-equilibrium characteristics of different stages of the coexisting system. With the increase in the Mach number, the nonequilibrium degree of the system is increased exponentially, and the degree of correlation almost exponentially decreases.