Models of rotating compressible convection

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The vast majority of geodynamo models treat the liquid core of the Earth as an incompressible fluid, despite the fact that the core’s density varies by about 20%. This project aims to elucidate the effects of the finite compressibility on convection through numerical simulations. Direct simulation of a compressible core at realistic parameters is not feasible. It is therefore proposed to study compressible convection in a simplified Cartesian geometry, paired with experiments in a gas filled cell in a centrifuge, in order to generate a general understanding of the effects of compressibility. The experiments are performed at the Laboratoire de Géologie de Lyon and can reach more extreme control parameters than the simulations. Only the simulations are the subject of this proposal. The simulations will be run for gases to allow comparison with the experiments, and for equations of state pertinent for condensed matter as they are relevant to geophysics. The most important quantities to be extracted from the simulations are the heat flux and the zonal flow. Zonal flows of alternating direction, inexistent in an incompressible fluid, appear in the compressible case. The transition from 3D to 2D convection induced by rotation will be studied, as well as changes in the flow field when the gas is replaced by a liquid as the convecting fluid.