Oil Flow Visualization of Reynolds Number Effect on Asymmetric Vortices at Forebody

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An oil-flow visualization experiment was conducted about the Reynolds number effect of asymmetric flow on an ogive-cylinder model in a range of Reynolds number from 0.13×106 to 0.81×106 at 50 degree angle of attack. And the results were quantitatively measured. The results showed that the laminar separation lines on both sides of the model were asymmetric in subcritical Reynolds number range; with increasing Reynolds number, the transitional separation with separation bubbles first occurred on the lower vortex side regardless of roll angles, but the boundary layer on the higher vortex side remained the laminar separation, this kind of asymmetric flow separation pattern was called the critical inception regime; With increasing Reynolds number into upper critical region, the transitional separation also occurred on the higher vortex side of the body and the separation lines on both sides became symmetric, this flow pattern was called critical regime. The results also showed that the transitional separation pattern on the higher vortex side developed from the rear to the front of the body, but the one on lower vortex side originated from the midst.