Inviscid and viscous vortex models for Richtmyer–Meshkov instability

We present simple inviscid and viscous vortex models for the Richtmyer–Meshkov (RM) instability, in the limit of fluids of the same densities. The evolution of the interface is driven by a row of alternating point vortices. A regularization method for the singular vortices is applied to the inviscid model for stable calculations. The regularized vortex model provides fine resolutions for the interface, improving previous results on the evolution of the RM instability. The point vortex model, for the inviscid fluid, is validated by comparing with the results of the full vortex sheet model. The viscous vortex model for the unstable interface is based on the multi-Lamb–Oseen vortices. We show that the viscous vortex model gives the main qualitative features of the evolution of the viscous RM instability.