Numerical simulation of turbulent flows over 2-D valleys using three versions of the k–ε closure model

The RUSVAL wind tunnel experiment on turbulent flow over two-dimensional model valleys was simulated in order to compare the behaviour of three versions of the k–ε closure model. Along with the standard version, two others were used in which the dissipation equation is modified to account for high shear and strain phenomena. The modifications do not dramatically increase the computational cost of simulation. For the gently sloping valley, no significant differences were observed among models. They provide a good reproduction of the mean flow and fair results for the turbulent kinetic energy. In the case of the steeper valley, where mean recirculation takes place, the improvement due to corrections is evident for the mean flow while for the turbulent kinetic energy the behaviour is strongly dependent on the flow region considered, probably because of a non-negligible effect of turbulent transport terms. From the Reynolds shear stress results, it seems reasonable that, even for the more gently sloping valley, advection and turbulent transport effects are not negligible. In view of this, the usual model equations should be coupled with a transport equation for Reynolds shear stresses.