Heat Transport and Dissipation in 2.5D Rotating Internally Heated and Cooled Convection

TL;DR

This study uses 2.5D numerical simulations to explore heat transport and dissipation in rotating internally heated convection, revealing diffusion-free scalings for heat transport at high Rossby numbers and highlighting differences from boundary-driven convection.

Contribution

It demonstrates that internally heated convection can serve as an efficient model for studying diffusion-free heat transport in rotating systems, with implications for astrophysical convection models.

Findings

Heat transport follows mixing length theory scalings at high Rossby numbers.

Velocity amplitudes show diffusion-limited scalings.

Internally heated convection has more thermal dissipation in the bulk.

Abstract

Models of astrophysical convection, such as mixing length theory, typically assume that the heat transport is independent of microphysical diffusivities. Such 'diffusion-free' behaviour is, however, not observed in numerical simulations employing standard fixed-flux or fixed-temperature boundary conditions, except possibly in extreme parameter regimes that are computationally expensive to achieve. Recent numerical and experimental work has suggested that internally heated and cooled convection can exhibit diffusion-free scalings in more numerically accessible regimes. Here, we present direct numerical simulations of 2.5D Cartesian rotating thermal convection driven by an internal heating and cooling function. The use of distributed heating and cooling functions alleviates sharp thermal boundary layers that would otherwise be present, allowing the flows to be simulated with modest computational resources. We show that for high Rossby numbers this set-up recovers mixing length theory scalings for the heat transport. The velocity amplitudes, in contrast, are observed to display diffusion-limited scalings. By comparing against boundary driven rotating convection, we show that internally heated cases have a larger fraction of their thermal dissipation occuring in the bulk of the fluid. We suggest this is connected to the increased convective efficiency observed in these cases. Our results indicate that 2.5D internally heated convection can be used as a computationally inexpensive test-bed to investigate some aspects of diffusion-free heat transport.