Assessment of the Harmonic Balance Method for Rotor Blade Performance Predictions

This paper presents an assessment of the harmonic balance method for rotor blade performance predictions. The harmonic balance method within the HMB3 solver of Glasgow University has been extended to the use with overset grids, and results are presented for the PSP and AH-64A rotor blades in hover and forward flight. The predictions are compared with results from steady-state and time marching simulations. In particular, the harmonic balance method is assessed for capturing key flow features, such as the strength of the advancing blade shockwave and retreating side blade dynamic stall. The limitations of the method are also discussed. The findings show that the harmonic balance method is a promising alternative to time-marching simulations due to a significant reduction in computational costs, leading to the potential use of high-fidelity Navier-Stokes methods in optimisation studies.