Effect of juncture fillets on double-delta wings undergoing sideslip at high angles of attack

Abstract

A flow visualization study of the vortical flow over a baseline double-delta wing model and a diamond-fillet double-delta wing model both with sharp leading edges was conducted in the Naval Postgraduate School water tunnel using the dye-injection technique. The main focus of this study was to observe the effect of juncture fillet on the vortex core trajectory, and vortex burst location on the wing surface at high angles of attack with sideslip angles. The data reported in this thesis is believed to be the first of its kind on the effect of juncture fillets on double-delta wings undergoing sideslip at high angles of attack. The results indicate that the strake vortex burst point moves upstream with increasing angle of attack at zero sideslip angle; but at constant angle of attack the windward side strake vortex burst location moves upstream and inboard while the leeward side vortex burst point moves downstream and outboard with increasing sideslip angle. Comparison of test results between the baseline model and the diamond-fillet model indicates a clear delay for the latter model in terms of both vortex core trajectory and breakdown location at high angles of attack with and without sideslip angle. The vortex breakdown data for the diamond-fillet model implies lift augmentation during sideslip motion, thus supporting the concept of flow control using fillets.