Sound generation by an in-flight thick airfoil with a cavity

Researchers have long examined the potential of using a thick airfoil with a cavity in civilian flights. Such airfoil concept is envisaged not only to provide a stronger wing box structure, but also produce a higher lift-to-drag ratio than that of conventional airfoil with same thickness. The later claim is achieved by trapping vortices in the vicinity of the airfoil surface during flight. Up till now most of the related studies are devoted to better understand the airfoil aerodynamic performance and provide a general picture how it is controlled by manipulating the trapped vortices in cavity. However, the sound generation of the airfoil has received only rare attention. This study aims to fill up this knowledge gap. This paper reports a numerical study of the sound generation of a thick NACA 0018 airfoil, installed with a wall-mounted cavity on suction surface, flying at a Reynolds number Re = 2 × 104using direct aeroacoustics simulation (DAS) approach with the CE/SE method. Numerical results clearly reveal that, compared to the ordinary airfoil, the thick airfoil with cavity gives a higher lift-to-drag ratio but lower sound generation by 2.5 db at least. This implies the thick airfoil with cavity is a promising approach of wing design of future aircraft that is required to perform better and be more environmental friendly.