Speaker
Description
Models of astrophysical convection, such as mixing length theory, generally assume
that the transport of heat and momentum is independent of microphysical diffusivities. Such “diffusion-free” behaviour is, however, often not observed in numerical simulations of stellar or planetary convection (in which either the flux, or a fixed temperature or entropy, is usually imposed at the boundaries). This makes it difficult to extrapolate the results of the simulations to actual stars or planets.
Here, I will discuss recent simulations of convection that do exhibit diffusion-free properties. The use in such simulations of distributed heating and cooling functions alleviates sharp thermal boundary layers that would otherwise be present, allowing the flows to be simulated with fairly modest computational resources. I will show that in a variety of settings, ranging from 2D Cartesian boxes to 3D, rotating spherical shells, this approach yields heat-transport scalings in agreement with a diffusion-free theory of convection. I will also show that some other aspects of the flow, including the differential rotation, are likewise independent of the diffusivities in some regimes. These results have promising implications for the development of realistic stellar and giant planet models.
