Thermal evolution of a metal drop falling in a less dense, more viscous fluid

Abstract

The initial thermal state of terrestrial planets was partly determined, during accretion, by the fall of iron drops in a liquid magma ocean. We perform axisymmetric numerical simulations of these falling dynamics and associated heat exchanges, for various drop initial sizes and ambient viscosities. Our parametric study shows that the thermal boundary layer thickness, the depth and time for equilibration, the Nusselt number, and the magma ocean volume affected by thermal exchanges, all scale as power laws of the Peclet number that deviate from the classical balances because of drop distortions.