Effect of blowing pattern through leading edge on flow structure of 45 degree swept delta wing

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2016
Günacar, Gökay
There has been an increasing interest in recent years in control of flow structure over non-slender delta wings, which are the simplified planforms of Unmanned Air Vehicles (UAV), Unmanned Combat Air Vehicles (UCAV), and Micro Air Vehicles (MAV). Different control approaches have been applied to alter the flow structure with particular interests in preventing stall and delaying vortex breakdown. Among different flow control techniques, blowing through leading edge of the wing has been commonly used due to its high effectiveness. In the present study, the effect of blowing pattern through the leading edge on flow structure of a 45° swept delta wing is investigated by employing surface pressure measurement and laser illuminated smoke visualization in a low-speed suction-type wind tunnel. The air injection, which is controlled by a solenoid valve and the flow meters, is performed from the leading edges at chordwise distances of x/C=0.16, 0.44, and 0.68. By adjusting the injection rates at each chordwise distance, three different blowing patterns, descending, uniform, and, ascending, are applied at dimensionless momentum coefficients of 0.005, 0.01 and 0.02. The experiments are performed at attack angles of 7, 13, and 16 degrees and at Reynolds numbers varying from 14000 to 75000. The results indicate that the blowing through leading edge successfully eliminates the three-dimensional surface separation, which occurs at relatively high attack angles. The effect of blowing pattern on flow structure is clearly evident for the corresponding cases in which the best performance is achieved by the descending blowing pattern. Furthermore, the results show that the blowing deteriorates the flow structure and moves the breakdown location toward upstream at relatively low attack angles where the leading edge vortex and its breakdown are apparent.