Transitions near the onset of low Prandtl-number rotating magnetoconvection

TL;DR

This paper studies how low Prandtl-number fluids start convecting under rotation and magnetic fields, revealing complex patterns and increased heat transfer near the onset, using simulations and models.

Contribution

It combines DNS and low-dimensional modeling to analyze convective onset and transitions in magnetoconvection with rotation, highlighting pattern formation and heat transfer enhancement.

Findings

Multiple flow patterns near convection onset for weak magnetic fields

Sharp increase in Nusselt number indicating enhanced heat transfer

Flow patterns and heat transfer explained by low-dimensional models

Abstract

We investigate the onset of convective instability and subsequent transitions near it in Rayleigh-B\'enard convection (RBC) of electrically conducting low Prandtl-number (Pr) fluids in the simultaneous presence of rotation about the vertical axis and external uniform horizontal magnetic field with free-slip boundary conditions. Both three dimensional direct numerical simulations (DNS) and low dimensional modeling of the system have been performed for the investigation. DNS results show a plethora of patterns near the onset of convection for weak magnetic field. Most interestingly, the Nusselt number (Nu) computed from the DNS data for relatively stronger magnetic field shows a sharp jump at the onset, indicating substantial enhancement of the convective heat transfer. The origin of these flow patterns, as well as the reason for a notable increase of heat transfer near the onset of convection, are then explained using low dimensional models constructed from DNS data.