On the acoustic and aerodynamic performance of serrated airfoils

Abstract

This paper is concerned with the aerodynamic and aeroacoustic performance of airfoils with serrated trailing edges. Although a great deal of research has been directed toward the application of serrations for reducing the trailing-edge noise, the aerodynamic performance of such airfoils has received very little research attention. Sawtooth and slitted-sawtooth trailing edges with specific geometrical characteristics have been shown to be effective in reducing the trailing edge noise over a wide range of frequencies. It has, however, also been shown that they can alter the flow characteristics near the trailing edge, namely the boundary layer thickness and surface-pressure fluctuations, and the wake formation. To better understand the effects of serrations, we shall carry out various acoustic and wind tunnel tests for a NACA6512-10 airfoil with various sawtooth, slitted and slitted-sawtooth trailing edge profiles. Flow measurements are carried out using PIV, LDV and hot-wire anemometry and the steady and unsteady forces on the airfoil are obtained using a three-component force balance system. Results are presented for a wide range of Reynolds numbers and angles of attack. The results have shown that the use of sharp serrations can significantly change the aerodynamic performance and wake characteristics of the airfoil.