The evaluation of the angle of attack effects on structure of diamond wing with sharp leading edge being equipped with LEX by using flow visualization

The flow behavior over a generic diamond wing was experimentally investigated in a smoke tunnel, using laser sheet technique. The effects of Leading Edge Extension (LEX) were also studied. The experiments were conducted at the velocity of 2.5 (m/s) and the angles of attack of 5 to 45 degrees. The results showed that a vortex structure was formed above the wing surface. Increasing the angle of attack intensified the size and strength of the vortices and the height of the vortex core to the wing surface as well. At a specific angle of attack, the structure of the vortices was changed rapidly and the vortex break down was occurred. The location of vortex break down moved toward the wing apex by increasing the angle of attack. The LEX caused formation of another vortex above the wing surface which was merged with the main wing vortex and formed a stronger one. The stronger vortex energized the boundary layer of the wing surface, delayed the flow separation and moved the break down further down-stream. Considered LEX also decreased the width of the wake region behind the wing, up to 14% compared to the original wing which can improve the aerodynamic performance of the control surfaces behind the wing.