Direct numerical simulation of tonal noise in sub- and transonic airfoil flow

Abstract

Tonal noise phenomenon is studied by Direct Numerical Simulation of the sub- and transonic flow around the symmetric NACA 0012 airfoil. A fifthorderWeighted Essentially Non-Oscillatory and a fourth-order explicit Runge-Kutta scheme are utilized. A main focus of this paper is the validation of the method and a grid study for an airfoil flow at a moderate Reynolds number. Therefore, the results of a Direct Numerical Simulation of subsonic flow are compared to experiments. Both, the results of the numerical and experimental flow show the tonal noise phenomenon. The interaction of the Tollmien-Schlichting waves and the trailing edge is studied visually enabling to easily understand the physical principles of the tonal noise phenomena. Additionally, for a transonic flow the non-linear pressure wave propagation, merging and frequency shift is considered.