Research On The Influence Of Surface Vibration On Airfoil Aerodynamic Noise

With the rapid development of aerospace and wind-power industry,aerodynamic noise problem is badly in need of solution.In fact,because of the flexibility of wind turbine blade,helicopter rotor and aircraft wing,bending-torsional coupled vibration may be caused by unsteady aerodynamic load in engineering application.This kind of surface vibration is bound to increase the disturbance of the incoming flow and affect the aerodynamic noise generation.In order to study how the different surface vibration will affect the aerodynamic noise,NACA0012 airfoil and straight wing are selected as the research model in this paper and the surface vibration is simplified as pitching,heaving and joint movement.The flow field is calculated by the DES method,meanwhile the noise prediction is based on the FW-H equation.The sound field of classical tandem cylinder is simulated and the numerical results are compared with the experimental results so as to verify the feasibility and accuracy of this method.In order to evaluate the impact of the surface vibration on the aerodynamic noise level,the aerodynamic noise of the static airfoil at different angles of attack are calculated and analyzed firstly.Then the influences of different vibration parameters on aerodynamic noise are studied,including vibration amplitude,frequency and phase relationship.In order to consider the three-dimensional effect,the influence of vibration wing on the aerodynamic noise is also studied and the numerical results of compared with the two-dimensional results.It turns out that: When the surface is moving in a single degree of freedom,the aerodynamic noise is most affected by the vibration frequency and the influences of the amplitudes of pitching and heaving are at the same level.The noise intensity is related to the turbulence of the flow field produced by airfoil motion and it increases as the amplitude increases,but the relationship with the vibration frequency is not monotonic.For the mixed motion,when pitching and heaving motions have 90°phase difference,the aerodynamic noise is the smallest.