A Numerical Study to Optimise Blowing Flow Control for Flap Side-Edge Noise Reduction

Abstract

A three-dimensional delayed detached eddy simulation was performed on a high-lift con guration consisting of a main element and a double-slotted ap. The objective of the computation was to optimise blowing ow control applied to the ap side-edge. The blowing slots were located on the suction, side-edge and pressure surfaces of the ap sideedge. The jet momentum coe cient, jet location, and jet orientation were varied in order to determine the optimum settings for maximum noise reduction. The best con gurations were identi ed by comparing the ow elds in terms of the reduction in strength of the side edge vortex and displacement of the vortex from the ap surface. A Ffowcs-Williams and Hawkings integral method was used to compute the far eld noise from the unsteady ow eld. The best ow control con gurations were compared to identify their ap sideedge noise reduction potential. The ow eld results showed that there was an optimum blowing momentum coe cient of 2:49 10 , beyond which any further increase in the blowing momentum coe cient resulted in only a small increase in the displacement of the ap side-edge vortex. Blowing air only from the pressure surface of the ap side edge was undesirable as it moved the side-edge vortex closer to the ap surface whereas blowing air from the suction surface or the ap side-edge surface were both e ective at displacing the side-edge vortex. Computations were performed on each blowing con guration with di erent jet orientation angles with respect to the surface. The results identi ed that the con gurations in which air was blown obliquely from both the suction surface and the sideedge were the most e ective at displacing the side-edge vortex. Based on the results from the parametric computations, the recommended ow control was blowing air simultaneously from the suction surface and side surface obliquely. This ow control con guration reduced the overall noise from the ap side-edge by up to 4.8 dB and the total noise by up to 4.5 dB.