Aerodynamic/Structural/Acoustic Prediction of HART II Rotor Using Weakly Coupled CFD-CSD Analysis

Many investigations have been conducted to understand blade-vortex interaction (BVI) and the resulting acoustic noise so that they may reduce the rotorcraft's noise. For an accurate understanding of BVI, complex motion of an elastic rotor blade needs to be predicted. Japan Aerospace Exploration Agency (JAXA) has developed its own CFD analysis using both flow and acoustic solvers to predict BVI noise. At the same time, Seoul National University has developed its own CSD that may analyze the non-linear deformation in an elastic beam. Upon these backgrounds, separate CFD and CSD analyses are conducted. And, then a combined analysis of both is attempted using a loose coupling method. Such combined analysis is performed regarding a steady-state flight such as hover. The next step is to analyze a periodic steady-state flight condition such as forward flight. In this paper, HART II blade flapping motion in a forward flight acted upon by periodic airloads and collective pitch angle is predicted using a similar analysis as is used in hover. But the response phase is quite different from that observed in the experiment. Thus, a further consideration upon the periodic excitation forces and the blade response will be required in the foregoing CFD/CSD computation for forward flight.