Rotor Blade Structural Loads Analysis Using Coupled CSD/CFD/VVPM

In this paper, a hybrid flow solver was coupled with a multi-body finite element computational structural dynamics (CSD) solver to analyze rotorcraft structural loads in several forward flight conditions. The hybrid flow solver consists of a near body computational fluid dynamics (CFD) solution and the state-of-the-art viscous vortex particle method (VVPM). The near body CFD solver concentrates on the body surface airloads computation with a dramatically reduced number of grid nodes and, hence, a significantly reduced computational time. VVPM addresses the complicated rotor wake and solves the wake vorticity dynamics using a grid-free Lagrangian representation. The coupled CSD/CFD/VVPM was used to predict the rotor blade structural loads for a UH-60A rotor in different forward flight conditions. The analysis results demonstrate that the hybrid solution helps to significantly improve the predicted structural loads at a representative low speed flight condition. Specifically, the hybrid solution produces an excellent correlation for the 3=rev flapwise bending moment and the 4=rev torsional moment where most of the previous non-hybrid CSD/CFD solvers show significant discrepancies when compared with the measured data.