Effect of three-dimensional shear-layer structures on slat cove unsteadiness

Numerical simulations are used to investigate the local and global dynamics of large-scale, three-dimensional vorticity structures within the free shear layer originating from the slat cusp of a multielement airfoil configuration. Results indicate that accounting for the local three-dimensionality of flow fluctuations leads to substantially improved agreement between the computed unsteady near-field solution and wind tunnel measurements based on particle image velocimetry. Analysis of simulation data indicates the potential significance of high intensity turbulent fluctuations near the reattachment location along the slat lower surface toward the generation of broadband slat noise. The computed acoustic characteristics, in terms of the frequency spectrum and spatial distribution within short distances from the slat, resemble the previously reported, subscale measurements of slat noise.