Visualization of supersonic flow around a sharp-edged, sub-boundary-layer protuberance

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Innovations in conventional surface and planar laser scattering visualizations revealed complex structures in the Mach 2.5 flow past a sharp-edged, sub-boundary-layer ramp with swept sides that is one type of micro vortex generator (MVG). The incoming flow separated over the leading edge despite the ramp angle being below the threshold for incipient separation. The separation produced a weak trailing horseshoe vortex system. The flow over the top of the MVG separated off the slant edges to produce a large primary vortex pair. Extra details were revealed at the trailing edge with at least two pairs of singularities. Vortex filaments spring from these singularities. Symmetry breaking from the confluence of the two primary vortices was observed as an unsteady wake to result in a train of possibly ring or hairpin vortices trailing downstream.

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    Use of fluorescent pigments with ultraviolet light has been reported previously (Merzkirch et al. 1987).


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The author thanks Adam Pierce and Yusi Shih for their assistance with the experiments, and Prof. Chaoqun Liu and Dr. Qin Li for their insightful comments. Support of the research by an AFOSR Grant No. FA9550-08-1-0201 monitored by Dr. John Schmisseur is gratefully acknowledged.

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Correspondence to Frank K. Lu.

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Lu, F.K. Visualization of supersonic flow around a sharp-edged, sub-boundary-layer protuberance. J Vis 18, 619–629 (2015).

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  • Protuberance
  • Flow topology
  • Viscous–inviscid interaction
  • Flow visualization