The effects of magnetic fields on Kelvin–Helmholtz instability (KHI) in two-dimensional multi-mixing layers are investigated considering both transverse and longitudinal magnetic fields. The effects of density ratio on the KHI of multi-mixing layers are also considered. The governing magnetohydrodynamic (MHD) equations are numerically solved using a validated non-splitting corner transport upwind (CTU) + constrained transport (CT) algorithm. Simulation results indicate that gravity exerts a stabilizing effect when density increases from top to bottom, which is consistent with existing research. Furthermore, increasing the density ratio gives rise to localized regions of elevated vorticity under the effect of gravity. Additionally, both transverse and longitudinal magnetic fields can significantly suppress KHI and cause vorticity deposition at mixing layer interfaces. However, unlike transverse fields, longitudinal magnetic fields induce vorticity layer separation with vorticity-free zones between separated layers, and even weak longitudinal fields exert notable effects. Furthermore, larger density ratios reduce the magnetic field strength needed to fully suppress KHI. Mechanistic analysis from the perspective of magnetic forces identifies magnetic pressure as the main cause of vorticity deposition. The magnetic tension of the transverse magnetic field exerts an anti-bending effect on mixing layer curling, while the magnetic tension of the longitudinal magnetic field forms a “magnetic tension ring” in the vorticity layer, thereby causing the separation of the vorticity layer and the formation of vorticity-free zones.
Zhao et al. (Sun,) studied this question.