Abstract
It is well known that the application of active flow-control strategies has the potential to increase the efficiency of many devices when compared to static actuator concepts. However, many aspects of the flow-control process are not well understood. In the case of pneumatic vortex generators the importance of coherent structures and their interaction with turbulent boundary layers remains an open question. A flat plate experiment was performed to determine the dynamic evolution of the induced vortex structures using phase-locked stereoscopic Particle Image Velocimetry. The qualification of the actuator system was performed by means of the time-resolved Particle Image Velocimetry measurements of the jet flow. The results show that an initial overshooting of the jet velocity dominates the unsteady start-up process, which results in a vortex structure of larger size and impact. This effect differs essentially from the case of steady blowing. In addition, the ability to shift high-momentum fluid into the near-wall region is a result of strong mixing combined with a minimum distance between the vortex core and the model surface.
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Ortmanns, J., Bitter, M. & Kähler, C.J. Dynamic vortex structures for flow-control applications. Exp Fluids 44, 397–408 (2008). https://doi.org/10.1007/s00348-007-0442-8
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DOI: https://doi.org/10.1007/s00348-007-0442-8