Systematical research on the aerodynamic noise of the high-lift airfoil based on FW-H method

Abstract

In numerical computation of aerodynamic noises, the solution accuracy of flow fields has an obvious impact on detailed computation of eddy turbulence and acoustic results. In this paper, LES (Large Eddy Simulation) was used to conduct numerical simulation of flow fields of three-dimensional high-lift L1T2 airfoil. Unsteady flow field data on the solid wall face was extracted as the noise source. The integration method FW-H (Ffowcs Williams-Hawkings) was used to compute far-field noises. The numerical computation method was verified by experiments. Results show that: the numerical computation method used in this paper can provide an accurate solution for computing far-field aerodynamic noises. Finally, based on the verified numerical model, contribution amounts made by each high-lift airfoil component to noises as well as major factors affecting aerodynamic noises were analyzed. Computational results show that: the leading edge slats generated aerodynamic noises mainly because of the unsteady waves which were caused by the grooves between the slat and main wing, as well as small wake eddies generated on the trailing edge of slats; flaps generated aerodynamic noises mainly because of mixing between high-frequency small-scale eddies and low-frequency large-scale eddies caused by flow separation around the wing flaps. Acoustic directivity of leading edge slats and trailing edge flaps showed an obvious dipole characteristic. For both of them, the sound pressure levels reached the maximum value in the direction perpendicular to the chord line.