Large-Eddy Simulation of a Single Airfoil Tip-Leakage Flow

Abstract

A large-eddy simulation is performed on a single nonrotating airfoil with tip gap in order to highlight the noise sources in the tip-leakage flow. The geometry is composed of a NACA 5510 airfoil (5% camber, 10% thickness) mounted between two flat plates, with a 10 mm tip gap between the airfoil and one of the plates. The Reynolds number based on the chord is 960,000 and the Mach number is 0.2. The aerodynamic results from the simulation show the formation of the tip-leakage vortex and the interaction of the turbulent structures that exit the gap with the external flow near the trailing edge. Then, a Ffowcs Williams and Hawkings analogy is used to compute the far-field noise levels and an acoustic decomposition is performed to highlight the main surface contributions to the tip-leakage noise. The numerical simulation shows very good agreement compared with experiments and allows identification of the main noise source in the tip gap. The main noise source results from the interaction of the turbulent structures created in the tip gap close to the pressure side corner with the suction side tip edge. The scraping of turbulent structures along the tip edge is shown to be an efficient noise mechanism.