Numerical analysis on the high-speed impulsive noise propagation characteristic of helicopter rotor in the presence of strong shear flow

Abstract

Based on the Linearized Euler Equations (LEE) and the Computational Fluid Dynamics (CFD) technique, the propagation characteristics of helicopter rotor High-Speed Impulsive (HSI) noise in non-uniform flowfield are simulated and analyzed. A Hybrid Computational Aeroacoustics (HCAA) method for solving the sound field of rotor is first developed. The acoustic source region is simulated by solving Navier-Stokes equations, and the acoustic near-field is simulated by solving LEE based on the Runge-Kutta Discontinuous Galerkin (RKDG) method. The numerical analysis method is then validated through comparisons with experimental data, and the aeroacoustics characteristics of the UH-1H rotor are calculated. Afterwards, the propagation characteristics of HSI noise in the wind tunnel are calculated, and the “trap” effect of the shear layer on HSI noise is determined. Finally, the peak negative pressure, time-averaged acoustic energy, and instantaneous perturbed pressure field are analyzed in detail, and some conclusions are drawn. In jet flow, the HSI noise energy is reinforced, and the time of the peak negative pressure is significantly advanced. In still air, the HSI noise energy is attenuated, and the time of the peak negative pressure is slightly delayed. These investigations offer valuable data for developing advanced theoretical correction method to consider the effect of shear layer on rotating acoustic source.