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 usually focus on the aerodynamic performance of the airfoil and provide a general picture how it is controlled by manipulating the trapped vortices in cavity. However, the aeroacoustics of the airfoil has received only a little attention, especially the relationship between the airfoil aerodynamics and the sound generation. Therefore, this study aims to fill up this knowledge gap. This paper reports a numerical investigation of the sound generation of a thick NACA 0018 airfoil, installed with a cavity, flying at a Reynolds number Re = 20,000 using direct aeroacoustics simulation (DAS) approach with the CE/SE method. Furthermore, we will compare the numerical results with those from the same airfoil without cavity to highlight the possibility of achieving weak sound generation, but with airfoil lift increase.