ACOUSTIC CONTROL OF SEPARATED FLOW OVER A 2-DIMENSIONAL AIRFOIL AT DISTURBED INCOMING FLOW

The effects of disturbed incoming flow on the acoustic control of separated flow over a 2-dimensional low speed airfoil under high incidence have been investigated experimentally,including the benefits of acoustic excitation,the influence of parameters of exciting sound,and the variation of flow parameters in the boundary layer.The testing results indicate that,the flow velocity fluctuation of Large Scale Organized Structure Vorticity (LSOSV) v l and the benefit of turbulence intensity in the boundary layer u ' a/U ∞,the benefit of lift coeffecient,induced by exciting sound,will rapidly decrease along with the increase of turbulence intensity in the incoming flow.But the effective threshold value of sound pressure level will still enlarge gradually.It is also shown that,because of the rapid attenuation of oscillating velocity amplitude △ U ∞/U ∞ along the flow direction at natural flow field without exciting sound,the oscillating incoming flow has no effect on the benefits of acoustic excitation for the low speed 2-dimensional airfoil by and large.