Abstract
To clarify the mechanism for aerodynamic sound to be generated from an airfoil in a flow with turbulence, numerical simulations have been carried out for a flow around an airfoil subjected to the wake of a circular cylinder. The test airfoil has the NACA0012 profile with a chord length of 150 mm and a spanwise length of 7.5 mm, and it is set at angle of attack of 9 degrees. The wind velocity is set to 30 m/s, which results in an airfoil Reynolds number of 3.0×105. The circular cylinder is set 100 mm upstream of the leading edge of the airfoil. The numerical simulations are composed of large eddy simulation (LES) and aeroacoustical simulations that solves the Lighthill equation in the frequency domain with the Lighthill tensor computed by the afore-mentioned LES as the acoustical source terms. The sound pressure level is also computed by the Curle’s equation with the fluctuation in the fluid force computed by the LES as the acoustical source. When they flow near the leading edge of the airfoil, the vortices in the cylinder wake are stretched due to the acceleration of the main flow, forms strong source of sound, and radiated intense sound in the upstream direction.
