An experimental investigation on asymmetric vortex breakdown flow over three delta wings with sweep angle of 85°, 80°, and 70° was carried out in a wind tunnel at high angles of attack and Reynolds number of using particle image velocimetry and pressure measurement techniques. First, vortex breakdown flow over delta wings with different sweep angles was measured to confirm the asymmetric flow phenomenon and its formation conditions. Time-averaged vortex breakdown flow over the 70° swept wing was found to be symmetric, whereas flow is asymmetric over the 80° and 85° swept wings. Instability due to crowding together of both leading-edge vortices is the cause of asymmetric vortex breakdown flow. Second, a special test that two nose sections with the same size and shape, named NT1 and NT2, was used to explore the effect of manufacturing imperfection of nose on the asymmetry of vortex breakdown flow was designed. Unpredictable manufacturing imperfection at the nose tip was found to be key natural perturbation of the instability, which led uncertain asymmetric vortex breakdown flow. Finally, the effects of an artificial spherical microperturbation with diameter of 0.2 mm fixed at the nose tip were examined to confirm the nondeterminacy of natural perturbations. With artificial microperturbations, rolling moment induced by asymmetric vortex breakdown flow can be controlled in a skillfully deflected manner.
Experimental Investigation of Asymmetric Vortex Breakdown Flow Control by Microperturbation over Highly Swept Wings
Journal of Aerospace Engineering ; 31 , 6
2018-08-13
Article (Journal)
Electronic Resource
Unknown
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