On the character and mechanics of flow-induced wall-mounted finite airfoil noise production

Abstract

A major source of noise involves flow interaction with wall-mounted attachments such as fins, guide vanes, aircraft airframe components, and wind turbine blades. In a simplified sense, these objects can be viewed as wall-mounted airfoils of finite length. A wall-mounted finite airfoil has one end immersed in the free stream and the other end fixed to a wall that is subject to a developing boundary layer. The free-end and wall junction introduce three-dimensional flow structures into the wake that affect noise generation in ways that are not yet fully understood. The primary goal of this research is to determine how airfoil end-effects and three-dimensional aerodynamics influence airfoil noise production. To accomplish this goal, anechoic wind tunnel studies have been conducted to determine the characteristics and mechanisms of flow-induced noise production for various wall-mounted finite airfoil configurations. The test models include combinations of airfoil profile shape, aspect ratio, angle of attack and free stream velocity. The motivation for this work is to gain a better understanding of sound generation from wall-mounted finite airfoils to aid future innovation in quiet aerodynamic design and optimisation.