Evolution of the rotating Rayleigh-Taylor instability under the influence of magnetic fields

Abstract: The combined effects of imposed vertical mean magnetic field (B0) and rotation on heat transfer phenomenon driven by the Rayleigh-Taylor instability are investigated using DNS. In the hydrodynamic (HD) case (B0 = 0), as the rotation rate f increases from 4 to 8, the Coriolis force suppresses the growth of mixing layer height (h) and u3', leading to a reduction in heat transport. The imposed B0 forms vertically elongated thermal plumes that exhibit larger u3' and efficiently transport heat between hot and cold fluid. Therefore, we observe an enhancement in heat transfer in the initial regime of unbroken elongated plumes in f=0 MHD cases compared to the corresponding HD case. In the mixing regime, the flow is collimated along the vertical magnetic field lines due to imposed B0, resulting in a decrease in u3' and an increase in growth of h compared to f=0 HD case. This increase in h enhances heat transfer in the mixing regime of f=0 MHD over the corresponding HD case. When rotation is added along with imposed B0, the growth and breakdown of vertically elongated plumes are inhibited by the Coriolis force, reducing h and u3'. Consequently, heat transfer is also reduced in rotating MHD cases compared to corresponding f=0 MHD cases. The heat transfer in rotating MHD cases remains higher than in corresponding rotating HD cases. This also suggests that B0 mitigates the instability-suppressing effect of the Coriolis force. The t.k.e. budget reveals the conversion of t.k.e., generated by the buoyancy flux, into t.m.e..