Airfoil noise measurements at various angles of attack and low Reynolds number

Abstract

Airfoils produce tonal noise when operated at low-to-moderate Reynolds number. It is particularly annoying to the human ear and is problematic for the design of fans, compressors, helicopter rotors and unmanned air vehicles. Despite recent advances in the understanding of this phenomenon, there are still many unresolved aspects regarding the aerodynamic source generation mechanism. In this paper, the trailing edge noise characteristics of a NACA0012 airfoil at low Reynolds numbers (50,000 to 150,000) are presented. Experimental measurements show that the noise consists of a multitude of tones centered about a broadband component. Such noise spectra are not observed at higher Reynolds numbers. The effect of angle of attack and Reynolds number will be discussed along with possible source generation mechanisms.