Assessment of laminar-turbulent transition modeling methods for the prediction of helicopter rotor performance

Abstract

The influence of the laminar-turbulent transition on helicopter rotor performance in hover and forward flight is investigated by means of URANS simulations. Two different transition modeling approaches are assessed by comparison with available experimental data of the ONERA wind-tunnel scaled 7A rotor. The first one is based on semi-empirical transition criteria and the second one is the Menter-Langtry transport equation model. In hover, Menter-Langtry model slightly improves the prediction of the figure of merit, while transition criteria-based method gives an almost perfect agreement with the experiments. In forward flight, the unsteady motion of the transition obtained with criteria is in fairly good agreement with experimental data deduced from hot film measurements, while Menter-Langtry model shows more unexpected behavior. However, the rotor power predicted by both simulations is very similar. Although transition improves the rotor power prediction in forward flight, the error with respect to the experiments remains still significant.