Computational Fluid Dynamics Transition Models Validation for Rotors in Unsteady Flow Conditions

Abstract

Computational fluid dynamics transition models are evaluated for rotors in unsteady axial and in forward flight conditions. The study is carried out using CREATETM-AV Helios. Three transition models are considered: amplification factor transport (AFT), Langtry–Menter (LM), and the LM with a crossflow transition model. The LM model is modified to allow for Galilean invariance. The first rotor configuration is the German Aerospace Center (DLR) rotor tested in the Rotor Test Facility in Göttingen (RTG). It is a four-blade, 2.13-foot-radius rotor in axial flow with pitching blades, operating at Reynolds numbers of and at three quarter radius, for the two test cases studied. The second configuration is the pressure-sensitive-paint rotor. It is a model-scale, 5.58-foot-radius, three-blade rotor operating at a high-advance-ratio, high-thrust forward flight condition and a hover Reynolds number of at three quarter radius. For both rotors, good agreement is found between the computed and the measured transition locations, obtained using the differential infrared thermography technique. The AFT and LM models produced remarkably consistent predictions. The crossflow model predicted an early transition onset compared with the test data.