ON THE FLUID MECHANICAL AND ACOUSTIC MECHANISMS OF SERRATED LEADING EDGES

Abstract

SUMMARY On the basis of experimental investigations, numerical flow simulations were carried out on a fan with leading edge serrations. The fan operates in turbulent inflow and a good agreement with the experiment could be achieved. It was found that leading-edge serrations generate longitudinal vortices that are temporally and spatially stable and thus improve the flow over the airfoil. In addition, a vortex could be generated which reduces the leakage across the tip gap. The stabilization of the flow over the blade reduces the pressure fluctuations on the blade surface, which in turn leads to less sound radiation. The found physical mechanisms of serrations have great effects on simple fan geometry, but are reduced in optimized fans, which weaken their positive effects on the flow field and the sound emission.