Numerical Assessment of the Effect of Leading Edge Vortex Breakdown on the Lateral-Directional Derivatives at High Angles of Attack

Document Type : Original Article

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Lecturer at the Department of Mechatronics, Pyramids High Institute of Engineering & Technology, 6th October City, Cairo, Egypt.

Abstract

Modern fighters design is characterized by slender wings of sharp leading edges (L.E.) and sharp-sided fore-bodies to provide extremely strong L.E. vortices and thus allowing maneuvering at high angles of attack (AoA), and besides improving stealth characteristics as well. These design features caused remarkable changes in the behavior of lateral-directional derivatives at high AoA. In this paper, the behavior of lateral-directional derivatives at high AoA is investigated for a generic fighter model that employs the sharp-edged trend using computational fluid dynamics (CFD). The study concluded that vortex breakdown is a key-element in deteriorating the lateral-directional stability at high angles of attacks. Also, asymmetric lateral-directional aerodynamic loads at high angles of attack were observed as well. The study also observed higher sensitivity to sideslip at high AoA; a small sideslip angle would destabilize the lateral-directional dynamics. The computed lateral-directional derivatives were utilized to predict the onset value of AoA for wing rock with very good agreement.

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