Effect of Passive Bleeding on Flow Structure over a Nonslender Delta Wing

The effect of passive bleeding on flow structure of a 45 deg swept delta wing is studied in a low-speed wind tunnel using techniques of laser-illuminated smoke visualization, surface-pressure measurements, and particle image velocimetry. Three different bleeding configurations are tested to identify the effectiveness of the control technique compared to a base planform for a broad range of attack angles 6 <= alpha <= 6deg at Reynolds numbers Re=3.5x10(4) and Re=10(5). The results indicate that all bleeding configurations alter the flowfield over the planform, where a proper bleeding induces significant improvement on the overall flow pattern. At sufficiently high angle of attack where pronounced surface separation appears on the base planform, the recovery of the vortical structures with significant increases in the magnitude of suction pressure coefficient -C-p, which implies the elimination of three-dimensional surface separation, is achieved with the corresponding bleeding configuration. On the contrary, at low attack angles, the bleeding causes reduction in the magnitudes of suction pressure coefficient -C-p in general, indicating a loss in suction performance of the planform. To conclude, the results confirm that the bleeding might effectively be used to eliminate the surface separation on nonslender delta wing.