Prediction of the rotor aeromechanics in descending flight using mixed variational geometrically exact beam model and CFD coupled analysis

Abstract

This paper presents prediction of the rotor aeromechanics for HART II experiment in a descending flight. The HART II was conducted to improve understanding of the Blade-Vortex Interaction (BVI) phenomena. For precise predictions of the aeromechanics of the HART II, CSD/CFD coupled analyses were conducted based on the delta load approach. In the CSD model, the mixed variational geometrically exact beam model was used to obtain the blade nonlinear behavior, and a CFD flow solver based on unstructured meshes was used for predicting the blade aerodynamic loads. The present beam model has advantages that displacements, internal forces/moments, and linear/angular momenta can be obtained directly. For the delta load approach, a finite-state dynamic inflow model was used to analyze trim condition for initial step in the present CSD model. The present results are compared with the measurement on the HART II rotor blades. The structural results show that the predicted flap deflection is quite similar with that of the measurement, but the torsional and lag deflections are under-predicted compared to those of the measurement.