Non-Boussinesq Low-Prandtl Number Convection with a Temperature-dependent Thermal Diffusivity

In an attempt to understand the role of the strong radial dependence of thermal diffusivity on the properties of convection in sun-like stars, we mimic that effect in non-Oberbeck-Boussinesq convection in a horizontally-extended rectangular domain by allowing the thermal diffusivity to increase with the temperature (as in the case of stars). Direct numerical simulations (i.e., numerical solutions of the governing equations by resolving up to the smallest scales without requiring any modeling) show that, in comparison with Oberbeck-Boussinesq simulations, the symmetry of the temperature field about the mid-horizontal plane is broken, whereas the velocity and heat flux profiles remain essentially symmetric. Our choice of the form of the temperature-dependent thermal diffusivity, which resembles the variation in stars, results in the temperature field that loses its fine structures toward the hotter part of the computational domain, but the characteristic large scale of the turbulent thermal superstructures, which are structures whose size is typically larger than the depth of the convection domain, continues to be largely independent of the depth. 

Email nyuad.spacescience@nyu.edu for more details.

Speakers

• Ambrish Pandey, NYUAD, Center for Space Science

In Collaboration with