The effect of different k- closures on the results of a micro-scale model for the flow in the obstacle layer

Abstract

A non-hydrostatic micro-scale model (MITRAS) is used to simulate the flow field over a beam. The model is run with a constant grid size of 1/5 times the beam height representing a relatively coarse resolution. Different types of k-ε closures are used, the standard-k-ε-closure and modified ones. A comparison of model results (mean values, turbulent kinetic energy and momentum fluxes) with wind tunnel data confirms the finding of earlier studies performed with models of higher resolution, that the standard-k-ε-closure overestimates the turbulent kinetic energy at stagnation points. The comparison with wind tunnel data reveals that the momentum fluxes are overestimated at stagnation points as well. A modification of the standard-k-ε-closure is introduced that reduces both, the modelled momentum fluxes and the turbulent kinetic energy at stagnation points.