Mass segregation by vorticity in 2D turbulence

We perform direct numerical simulations of the relaxation of two-dimensionnal turbulence skewed by a large density contrast. The initial collection of vortices is evolved in time together with an initially bimodal density field. The density contrast is large and corresponds to an Atwood number A = 2/3. Under the assumption of infinite Froude number, the misaligned density and pressure gradients trigger baroclinic sources and sinks of vorticity on density fronts. We analyse the biais in the mixing progress against a passive scalar reference simulation, starting from the same initial fields. Vortex carrying high-density fluid samples are be mass-depleted or break-up into filamentary debris. Meanwhile, intense vortices concentrate light-fluid samples and merge into large regions trapping almost unmixed low-density fluid. The interchange of mass between vortices and the interlacing medium is shown to be the result of different mechanisms embeded in vortex interactions.