Semi/empirical Transition Prediction and Application to an Isolated Rotor in Hover

Abstract

The transition prediction capability of two semi/empirical methods originating from fixed wing applications is studied for steady, rotary wing application. This includes the AHD criterion, and two variants of the Michel criterion. Both criteria are used with approximated boundary layer data, aiming to reduce dependency on near wall grid quality. The prediction methods have been implemented in the DLR’s structured flow solver FLOWer. A two-dimensional airfoil test case (Somers NLF(1)-0416) is used to study prediction accuracy, comparing three different turbulence models. A three-dimensional rotor test case at hover (DLR Bo 105 flight test) serves to validate the criteria’s computed transition locations. The influence of the criteria’s distinct laminar run-ning lengths on the rotor’s performance is shown by a relative comparison of figure of merit.