Abstract
Vortex structures in a separation-reattachment flow (separation bubble) formed at the leading edge of a blunt plate with right-angled corners were studied by a hydrogen-bubble flow visualization technique. Two kinds of hydrogen-bubble probes were employed; one is a single platinum wire of 0.05 mm diameter attached to the surface of the plate to visualize the instantaneous flow near the surface, while the other was a seven-wire rake which was used to visualize secondary flow patterns in the separation bubble. Reynolds number based on the thickness of the plate and the approaching velocity was 1200. Main results can be summarized as follows. (i) The secondary flow patterns have a typical spanwise distance which increases downstream, its value on the reattaching line being about 0.35 times the length of the bubble; (ii) there exist longitudinal vortices whose axis is inclined with respect to the longitudinal direction in such a way that their upstream side is nearer to the surface than their downstream side is.
