Utilization of Whale-inspired Leading-edge Tubercles for Airfoil Noise Reduction

Numerical studies are conducted to explore the noise reduction effect of leading-edge tubercles inspired by humpback whale flippers. Large eddy simulations are performed to solve the flow field, while the acoustic analogy theory is used for noise prediction. In this paper, a baseline airfoil with a straight leading-edge and three bionic airfoils with tubercled leading-edges are simulated. The tubercles have sinusoidal profiles and the profiles are determined by the tubercle wavelength and amplitude. The tubercles used in this study have a fixed wavelength of 0.1c with three different amplitudes of 0.1c, 0.15c and 0.2c, where c is the mean chord of the airfoil. The freestream velocity is set to 40 m/s and the chord based Reynolds number is 400,000. The predicted flow field and acoustic field of the baseline airfoil are compared against the experiments and good agreements are found. A considerable noise reduction level is achieved by the leading-edge tubercles and the tubercle with larger amplitude can obtain better noise reduction. The underlying flow mechanisms responsible for the noise reduction are analyzed in detail.