Effects of pulsed and continuous jet vortex generators in a turbulent boundary layer flow - an investigation by using two high-speed stereo PIV systems
2012
Continuous and pulsed jet vortex generators are well
known for their capability of inhibiting flow separation due
to enhanced mixing in turbulent boundary layer (TBL) flows. Jet vortex generators of adequate geometries produce
streamwise vorticity which in interaction with the TBL flow
increase the wall normal fluid transport. For a given ideal
configuration this transport depends on the ratio between jet
and the bulk velocity, but with a moderate jet velocity - even
in a pulsed mode- the wall normal fluid exchange can be
organized more efficient. Especially the shifts of high momentum fluid towards the wall produce regions of higher
wall-shear stress in comparison with the situation without jet
interaction. This is a favourable condition for TBL
flows with adverse pressure gradients e.g. at flaps of
high-lift-configurations to remain attached to the wall. The
efficiency of such stream-wise vorticity induced wall-shear
stress has been found to be increased for small (average)
distances of the vortex core to the wall. Elaborated DNS
of a strong jet vortex generator in a turbulent boundary layer
flow at a moderate Reynolds number show the complex
interaction between the stream-wise vorticity producing jet
flow wake and the new formation of turbulent structures in
the further development of the TBL.
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