Vortical Substructures in the Shear Layers Forming Leading-Edge Vortices

Abstract

Control of leading-edge vortex breakdown over sharpedged, slender, delta wings at high angles of attack is highly dependent on the knowledge of and the ability to detect or observe the principle characteristics of the phenomenon. Substantial theoretical, experimental and numerical research has focused on the characteristics of leading-edge vortices and vortex breakdown. However limited efforts have sought to understand the separating shear layers which roll up to form the leading-edge vortices. Increased interest in the role of vorticity in the vortex breakdown phenomena and recent advances in experimental measurement techniques have enabled more detailed analysis of the vortical flow field and the separating shear layer. The objective of this study is to characterize the vortical substructures in the separating shear layers forming the leading-edge vortices around a delta wing. Threedimensional Laser Doppler Velocimetry flow field measurements are realized in an ONERA subsonic wind tunnel around a sharp-edged, delta wing model with a 70°sweep angle and a root chord of 950mm at a chord based Reynolds number of 1.56xl0 6. The results provide a description of the structure and path of these vortical substructures around the leading-edge vortex cores. Additionally, information is obtained on the structure and path of the vortical substructures under the influence of along-the-core blowing which is used to manipulate the vortex breakdown location. This research is the next step towards a better understanding of the origin of the substructures and their influence on the leading-edge vortices and vortex breakdown.