Analytical, numerical and experimental investigation of trailing-edge noise reduction on a controlled diffusion airfoil with serrations

The present work investigates the broadband noise reduction that can be achieved using trailing-edge serrations. Experimental measurements for a controlled-diffusion airfoil at a Reynolds number based on the chord length of 1.5 × 105 have been collected in two open-jet wind-tunnels. Two simulations at a 8◦ geometrical angle-of-attack using the Lattice Boltzmann method reproduce the installation effects in the open-jet wind tunnels with DNS resolution around the clean and serrated airfoils respectively. Three analytical models for serrated trailing edges have been compared to this experimental and numerical data base. The simulations provide excellent agreement for the loading, wall-pressure fluctuations and far-field noise. The comparison of the clean and serrated airfoil allows identifying noise reduction of 5 to 15 dB in a limited range of frequency [800,4500] Hz. The turbulent wall-pressure statistics upstream of the serrations are not modified, and the effect of the acoustic scattering is negligible up to 10 kHz. Howe’s model overpredicts the observed noise reduction whereas Lyu’s and Ayton’s models provide similar gains in better agreement with the database. The latter model even closely matches the frequency range and the noise levels