Convection, dissipation, and rotation in simulations of stellar and planetary interiors and atmospheres

A wide range of fluid flows occur within astrophysical bodies such as stars and planets. In particular, convective flows are dominant throughout a significant portion of the structure of these objects, playing a key role in the transport of heat throughout their interiors. In a steady state, this convection must be maintained against any viscous and Ohmic dissipation that is present. Prior numerical studies on the nature of this dissipation have often lacked key physical components of the convection, such as the influence of rotation and stratification. Additionally, in planetary atmospheres the influence of the underlying interior convection zone on the resulting surface circulation has historically been underrepresented. This thesis examines idealised convective systems in an attempt to understand some of these influences. We present the first systematic numerical study of viscous dissipation and convection in a Cartesian layer in the highly stratified, rotating regime, and mixed fixed-entropy and fixed-flux boundary conditions. We find that while the influence of rotation does not affect the total amount of dissipation within the layer, the spatial distribution varies considerably as a result of the change in dynamical structure in the rotationally constrained cases. The obtained heat transport scalings show good agreement with those obtained in prior Boussinesq calculations and we define a new parameter which quantifies the spatial distribution of the dissipation and appears to provide a good indicator for whether a given system follows the rotationally constrained scalings or not. We also use the globally averaged value of dissipative heating to place constraints on the maximum (negative) value of the kinetic energy flux. Lastly, this thesis presents preliminary results on the influence of more physically motivated convective parameterisations on the atmospheric circulation of highly irradiated tidally locked exoplanets. Initial results show a significant weakening of the eastward equatorial jet, with an accompanying acceleration of the westward midlatitude jets. The thesis then concludes with a discussion of future work, along with accompanying proof-of-concept results.Science and Technology Facilities Counci