Dynamic Stall Simulations on a Pitching Finite Wing

Kurzfassung

Unsteady Reynolds-averaged Navier-Stokes computations were carried out on a pitching finite wing model using the finite volume solver DLR-TAU. The comparison with the experimental data reveals a good agreement, especially in the region of the first occurrence of stall. Discrepancies are observed in the blade tip region, where the flow in the numerical data shows a stronger separation along with larger hysteresis effects in contrast to the experiment. An investigation with different pitching frequencies revealed a change in the sequence of dynamic stall vortex formation in the spanwise direction. For the lowest frequency the propagation of the stall vortex starts at the wing tip and then spreads rootwards, whereas for the higher frequencies the first evolution of the dynamic stall vortex starts further inboard, subsequently propagating in tipward and rootward directions. An investigation using a γ-Reθt approach demonstrated that small differences can be attributed to transition, nevertheless these can give further insight in the physics of dynamic stall and improve the comparability with the experiment. A comparison with two-dimensional simulations shows strong similarities in the sections where the vortex starts to evolve and large differences in the surrounding areas.