Separation control by an array of vortex generator jets: Part 2. Pulsed jets
(English)Article in journal (Other academic) Submitted
The effect of longitudinal vortices produced by an array of steady jets on a separation bubble was examined experimentally. In the experiment an adverse pressure gradient causes the turbulent boundary layer on a at plate to separate. The jets are originating from ori ces in the wall and are directed 45° from the wall and 90° from the mean ow direction. In the centre of the separated region, particle image velocimetry (PIV) is used to measure the momentum increase near the wall that the vortices produce. The geometry was xed, but the ratio of jet velocity Ujet to the free stream velocity, the pulsing frequency and the duty cycle were varied. It was shown that to achieve maximum control e ect the injected mass ow should be as large as possible, within an optimal range of jet velocity ratios. For a given injected mass ow the important parameter was shown to be the injection time t1. A non-dimensional injection time is de ned as t+ 1 = t1Ujet /d, where d is the jet ori ce diameter. Here, the optimal t+ 1 was in the range 100-200.
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-9839OAI: oai:DiVA.org:kth-9839DiVA: diva2:133541
This work is part of a cooperative research program between KTH and Scania CV. QS 201203282009-01-122009-01-122012-03-28Bibliographically approved