Numerical Investigation of Unsteady Boundary Layer Transition on a Dynamically Pitching Rotor

Unsteady boundary layer transition predictions are performed on a four-bladed rotor in hover using a computational fluid dynamics approach. Simulations are performed using the NASA OVERFLOW 2.3 solver with hybrid RANS/LES and laminar-turbulent transition modeling. Solutions are based on a hover tip Mach number of 0.143 with prescribed dynamic pitching conditions. The configuration is based on experiments performed at the German Aerospace Center (DLR)in the 1.6-mx3.4-m wind tunnel in the rotor test facility (RTG). Computational methods and grid generation are described. The rotor flowfield is analyzed and the effect of transition modeling on unsteady boundary layer transition prediction is assessed. Laminar-turbulent transition predictions and rotor performance are compared to experimental measurements obtained at the DLR RTG.