Effects of sweep angles on turbulent separation behaviors induced by blunt fin

An experimental study was conducted on turbulent separation behaviors induced by blunt fins with different sweep angles at Mach number 6.0. The Nano-particle based Planar Laser Scattering technique (NPLS) was applied to visualize the flowfield, complemented by pressure tests. Sweep angles of the fins were 10°, 20°,…,60°, with the same leading edge diameter of 10 mm. Fine structures of the interference flowfield induced by blunt fins have been obtained, including the shock systems and vortexes. It was found that the features and shapes of the detached shock depended on sweep angle. When sweep angle < 50°, the detached shock appeared as the form of trailing shock, and the supersonic jet with its reflection could be observed. The detached shock would be curved for the 50° and 60° fins and became a transmitted shock. The Scale-Invariant Feature Transform (SIFT) was successfully applied to obtain the velocity field from NPLS images, and the extent of the separated region was found to decrease with increasing sweep angle. No separation appeared as sweep angle > 30°. Two peak values were detected on the centerline pressure distribution. The first peak did not rely on sweep angle, while the second peak value decreased with increasing sweep angle.