Research Article

Experiments in Fluids

, Volume 44, Issue 3, pp 397-408

First online:

Dynamic vortex structures for flow-control applications

  • Jens OrtmannsAffiliated withInstitut für Strömungsmechanik, Technische Universität Braunschweig Email author 
  • , Martin BitterAffiliated withInstitut für Strömungsmechanik, Technische Universität Braunschweig
  • , Christian J. KählerAffiliated withInstitut für Strömungsmechanik, Technische Universität Braunschweig

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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.