Evaluation of airload prediction methodologies using BH-360 test data

A detailed analysis of two airload prediction methodologies is proposed in this paper. The numerical methods used at the U.S. Army (AFDD) and at the French ONERA to compute the flowfield around the main rotor of a helicopter are described. In hover condition, these methods consist of an Euler solver for ONERA and a full potential code using a velocity decomposition scheme to convect the wake at U.S. Army. For forward flight conditions, both organizations use a full potential method initialized by the trim conditions calculated by a full aeroelastic computation. For low speed cases, where Blade-Vortex Interactions occur (descent flight), a free wake model is used. The results obtained by these methods are compared to wind tunnel test results obtained with the BH-360 rotor. The best comparisons with experiment are obtained in high speed forward flight, where shown that the differences between calculations and experiment are a direct consequence of the wake geometry predictions. Finally, in hover, the computed pressure distributions correlate reasonably well with experiment, although the total lift significantly differs from the measurements.