Large eddy simulations of compressible convection

Large-eddy simulation (LES) technique has been applied to two-dimensional compressible convection in a plane-parallel layer of ideal gas with intermediate density contrast. The general flow patterns consist of a series of rolls in the horizontal which are coherent throughout the entire vertical domain, much like findings by a number of investigators. The horizontal component of the subgrid-scale (SGS) force appears to enhance fluctuations of pressure and density, which in turn cause the resultant force, say fpg arising from pressure gradient and gravity terms, to increase in magnitude in such a way that fpg, besides balancing the inertial terms, can essentially offset the vertical component of the SGS force. Consequently, compared to a solution obtained omitting the SGS terms, the flow field of the LES solution only shows moderate differences. There is some indication that the overall SGS effect tends to reduce the asymmetry between the vertical flows in the interior of the domain while enhancing it in the base region.