Non-Boussinesq Rolls in 2d Thermal Convection

TL;DR

This paper investigates non-Boussinesq convection rolls in a 2D circular cell with heating and cooling at opposite edges, revealing analytical and numerical solutions for convection patterns beyond the Boussinesq approximation.

Contribution

It provides the first analytical and numerical analysis of non-Boussinesq convection rolls in a 2D circular geometry with tilt-dependent gravity effects.

Findings

Four symmetrical convection rolls are identified.

Purely conductive state is impossible with gravity present.

Analytical expression for convection rolls is derived.

Abstract

A study of convection in a circular two dimensional cell is presented. The system is heated and cooled at two diametrically opposed points on the edge of the circle, which are parallel or anti-parallel to gravity. The latter's role in the plane of the cell can be changed by tilting the cell. When the system is in a horizontal position, a non-trivial analytic solution for the temperature distribution of the quiescent fluid can be found. For a slight inclination, the projection of gravity in the plane of the cell is used as a perturbation parameter in the full hydrodynamic description, as the Boussinesq approximation is inadequate. To first order, the equations are solved for the stationary case and four symmetrical rolls become apparent, showing that a purely conductive state is impossible if gravity -however small- is present; an approximate closed analytical expression is obtained, which describes the four convection rolls. Further analysis is done by a direct numerical integration. Comparison with preliminary observations is mentioned.