Numerical Investigation of Turbulence Transition Models for the Prediction of Helicopter Rotor Performance in Hover

The capabilities of two different laminar-turbulent transition models are evaluated for the prediction of the PSP rotor performance in hover. The first transition model originates on non-local semi-empirical transition criteria that are calculated on the basis of the history of boundary layer quantities along the wall streamlines. The second one is the Langtry-Menter model that consists in two additional transport equations based on a local transition criterion. The same numerical methods and same post-processing are used with the elsA CFD solver in order to have a fair comparison between the models. Both transition modeling technics provide a good agreement with the experimental measurements concerning the transition position on the upper side of the blade. On the lower side, the predictions are less satisfactory. Transition criteria approach gives good trends while Langtry-Menter results seem to be polluted by the tip vortex flow. A grid sensitivity study shows that Langtry-Menter model requires very fine grid in order to predict the expected behavior while transition-criteria approach is less affected by the grid resolution. In terms of rotor performance, both approaches predict the experimental measurements, Langter-Menter tending to slightly overestimate the Figure of Merit where transition criteria approach slightly underestimates its value.