An experimental investigation of the flow in and around a separated region immediately downstream of a blunt base in swirling flow is presented. The structure of the base wake bubble is analyzed; it is found to be entirely different from that of a base wake in linear flow. It appears to be governed by the matching of two zones of flow. The inner flow follows an S shaped channel formed by stationary regions of closed streamlines (toroidal vortices). It is driven by the pumping action of the Ekman boundary layer on the base. The outer flow envelops the inner region. The base wake bubble is not closed in the usual sense although it exhibits an identifiable "throat" which terminates the region containing reverse flow. Downstream of the throat the flow has the structure of a swirling wake. At sufficiently low upstream Rossby numbers, it can undergo vortex breakdown which results in the formation of a second, free region of closed streamlines.
|Original language||English (US)|
|Number of pages||12|
|State||Published - Oct 1 1972|
ASJC Scopus subject areas