Kinetic investigation of Kelvin–Helmholtz instability with nonequilibrium effects in a force field

The Kelvin–Helmholtz (KH) instability in a force field is simulated and investigated using a two-component discrete Boltzmann method. Both hydrodynamic and thermodynamic nonequilibrium effects in the evolution of KH instability are analyzed in two distinct states: interface roll-up and non-roll-up. It is interesting to note that there are critical thresholds for initial amplitude and Reynolds number, both of which are determined based on the vertical density gradient. Specifically, when the initial amplitude and Reynolds number exceed their respective critical thresholds, the interface undergoes roll-up. Conversely, if these parameters fall below their critical values, the interface fails to roll up. Moreover, the initial amplitude promotes the development of density gradients, mixing degree, mixing width, viscous stress tensor strength, and heat flux strength. In contrast, the Reynolds number enhances the evolution of density gradients but dampens the mixing degree, viscous stress tensor strength, and heat flux intensity. The effect of the Reynolds number on mixing width is analyzed as well.