Modification of RANS turbulence models for pressure induced separation on smooth surfaces using the DLR VicToria experiment

Kurzfassung

We present a turbulent boundary-layer flow experiment at a significant adverse-pressure gradient with pressure-induced separation on a smooth surface at a high Reynolds number. The experiment was performed by DLR within the internal project VicToria. We describe the design of the test case, the setup in the wind tunnel, and the measurement technique using large-scale particle imaging and Lagrangian particle tracking. We show the experimental results for the mean velocity and for the Reynolds stresses for the evolution of the flow from the zero-pressure gradient region into the adverse pressure gradient region. From the measurement data we motivate wall laws for the mean velocity and for the Reynolds stresses. Then we consider the differential Reynolds stress transport model SSG/LRR-ω. Based on the observation that the length-scale equation is not consistent with the assumed wall laws at adverse-pressure gradient, we propose a modification of the equation for the dissipation rate ω in the model, so that the modified model can predict the proposed wall law at adverse-pressure gradients. Finally we show the numerical results using the modified SSG/LRR-ω model. The modifications cause a reduction of the near-wall flow velocity at adverse-pressure gradients making the modified model more susceptible for flow separation. Both observations are in good agreement with the experimental data.