Blade shape optimization for HSI noise reduction and performance improvement of helicopter

A high speed impulsive (HSI) noise occupies much part of the loudest noise of helicopter. It is caused by the shock wave on a blade surface at the advancing side and limits high speed flight performance of helicopter. To reduce the HSI noise, the authors performed blade planform design by using an aero-acoustic analysis technique and an optimization method. As for the aero-acoustic analysis, CFD technique for aerodynamic analysis and Kirchhoff's method for the acoustic analysis were used. As for the optimization method, Kriging-based genetic algorithm (GA) model as a high-fidelity multi-objective optimization method was chosen according to the design problem. In the present research, design variables to define arbitrary blade planform and new design variable to describe airfoil transition were used to consider the aerodynamic performance and noise characteristic, simultaneously. The optimization results showed that optimum blades have improved aerodynamic performance and similar level of HSI noise characteristic compared to the optimum shape obtained in our previous research.