Integrated Optimization Analyses on Aerodynamic/Stealth Characteristics of Helicopter Rotor Based on Surrogate Model

Based on Computational Fluid Dynamics (CFD) method, electromagnetic high-frequency method and surrogate model optimization techniques, an integration design method about aerodynamic/stealth has been established for helicopter rotor. The developed integration design method is composed of three modules: 1) integrated grids generation: the moving-embedded grids for CFD solver and the blade grids for Radar Cross Section (RCS) solver are generated by solving Poisson equations and folding approach. 2) aerodynamic/stealth solver: the aerodynamic characteristics are simulated by CFD method based upon Navier-Stokes(N-S) equations and Spalart-Allmaras(S-A) turbulence model, and the stealth characteristics are calculated by using a panel edge method combining the method of Physical Optics(PO), Equivalent Currents(MEC) and Quasi-Stationary (MQS), and 3) integrated optimization analysis: based upon the surrogate model optimization technique with Full Factorial Design (FFD) and Radial Basis Function (RBF), an integrated optimization analyses on aerodynamic/stealth characteristics of rotor are conducted. It has been demonstrated that CFD and RCS method are effective by comparing the calculated pressure distributions of UH-60A rotor and scattering distributions of cone with the experimental data. Then scattering characteristics of the rotor with different blade-tip swept and twist angles have been carried out. Considering the modulation of rotor, time-frequency domain grayscale with strong scattering regions of rotor have been given. Simultaneously, the effects of swept-tip and twist angles on the aerodynamic characteristic of rotor have been performed. Furthermore, by choosing suitable object function and constraint condition, the compromised design about swept and twist combinations of rotor with high aerodynamic performances and low scattering characteristics has been given at last.