Numerical Optimization for Rotor Blade-tip Planform with Low HSI Noise Characteristics in Forward Flight

Based on CFD/FW-H_pds methods and hybrid optimization technique, an optimization design procedure for rotor planform with low HSI noise characteristics is established. In this solver, based on the moving-embedded grid methodology, a CFD simulation method for the aerodynamic characteristics of rotor is developed by solving the compressible Reynolds-averaged Navier-Stokes (RANS) equations. Among the optimization process, the high-qualified blade grids are generated by a high-efficient parameterized method. Additionally, the high-speed impulsive (HSI) noise characteristics generated by transonic helicopter rotor are analyzed through a robust prediction method based on FW-H_pds equations (Ffowcs Williams-Hawkings equations with penetrable data surface). Aiming at the minimization of the noise level in forward flight, optimization analyses based on the rotor blade with double-swept and tapered tip have been accomplished with the aerodynamic performance as constraints. The genetic algorithm and surrogated model based on Latin Hypercube Sampling (LHS) design and Radial Basis Function (RBF) are combined as a hybrid optimization technique. Compared with rectangular blades, it shows that the noise level of rotor with optimized blade-tip shape can be decreased obviously at the present calculating condition. For the rotor with optimized blade-tip, the HSI noise level can be reduced effectively due to its weaker transonic "delocalization" phenomenon in the region of blade-tip.