Highly Resolved Simulations of Turbulent Mixed Convection in a Vertical Plane Channel

Abstract

Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of turbulent mixed convection in a vertical plane channel have been performed with the open source finite volume code OpenFOAM. Since the agreement of the results of LES obtained with second order accurate central differences in space, implicit time Integration and the PISO method for the pressure-velocity coupling to data in the literature was rather poor, additional DNS were performed to identify sources of discretization errors in OpenFOAM. The comparison revealed errors associated not only with the used eddy viscosity an diffusivity subgrid scale turbulence models used for LES but also with the provided default discretization settings. Changing the latter, it turned out that applying an explicit Leapfrog time integration scheme together with a projection method for the velocity-pressure coulping and a fourth order accurate discretization considerably improved the DNS results. Thus, this combination is also recommended for future LES studies.