Numerical Simulation Of The Helicopter Aerodynamic Noise

With the further requirement of helicopter stealth, the noise of helicopter attracts more and moreattention. This paper aims to simulate the flow field and the noise far-field of the hovering helicoptersand helicopter rotor combined with the three-dimensional RANS equations and FW-H equations, toresearch the characteristics of sound field with different Mach numbers, and to analysis thereasonableness and accuracy of these methods, and to develop the common procedures. The majorcontributions of the author’s research are as follows:First of all, we simulate the unsteady flow of the hovering rotor with the three-dimension RANSequations. The flow field was simulated by the hybrid grid technique. We take the inertial coordinatesystem as a reference system, take the block rotated with time around the object, and use a stationaryblock in the far field, in order to develop the stationary surface and rotated surface during thesimulation of noise. What’s more, we simulate the flow field of hovering helicopters with oversetgrids, get the aerodynamic data for the prediction of noise.Secondly，we derive the FW-H equations with the theory of generalized functions, and solve theequations with the free-space Green’s function; we get a better robustness formula with Kirchhoffequation and its solution, namely K-FWH formula.Then, we propose a unified algorithm for the prediction of noise, and get the NOSPREforecasting process. This process uses a modular which integrates three kinds of noise predictionmethods, and it can be used to solve the aerodynamic noise in hovering state with fixed and rotatingsound surfaces.Lastly, we use a point source, UH-1H helicopter rotor hovering as the validation studies, toresearch the reliability and accuracy of the process, while we use the helicopter with Robin as anexpanding example, to get the noise data of the helicopter in hovering state.