Assessment of heat flux turbulence models for flows dominated by buoyancy effects

Abstract

Improved prediction of complex transport processes usually requires an application of advanced turbulence models. In some particular cases, such as environmental flows, where a variety of physical and thermodynamical processes may occur simultaneously, it is not an easy task to apply a consistent approach for all modelled variables of interest. Consequently, this suggests the use of simple model formulations. In seeking an acceptable turbulence model for the computation of buoyancy dominated turbulent flows, two variants of the modelled turbulent heat flux vector are presented and their performance in the simulation of the lifting of an atmospheric inversion is discussed. By these variants the turbulent heat flux is expressed in both algebraic and differential forms. In applying the algebraic heat flux turbulence model, it was necessary to solve the transport equation for temperature variance and retain its explicit influence in the derived algebraic heat flux model in order to obtain results of similar accuracy to those of the full differential heat flux model.