A numerical study of turbulent flows in backward-facing step geometries: A comparison of 4 models of turbulence

A numerical study of two dimensional separating and reattaching turbulent flows in plane backward facing step geometries with parallel and deflected walls. Closure of the Reynolds equations was achieved by four different models: kappa-epsilon modified kappa-epsilon algebraic stress and modified algebraic stress models. The kappa-epsilon model relates the Reynolds stresses to the mean rate of strain through the definition of an isotropic turbulent viscosity, whereas the more advanced algebraic stress model calculates the stresses from implicit algebraic relationships containing the stresses themselves, the mean rate of strain, and the turbulent kinetic energy and its dissipation rate. Modified versions of the models employ a new dissipation rate equation whose production term was made more sensitive to streamwise curvature effects. A new non-equilibrium wall function treatment was also incorporated into each model.