A Study on Promotion of the Near-Wall Turbulence Mixing by Phase Control of the Pulsed Vortex Generator Jet Row.

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A vortex generator jet in a turbulent boundary layr has been investigated, since it has a significant potential for the active control of boundary layr stall. The present project concerns the pulsed vortex generator jet through a single hole which generates periodic longitudinal vortices in the boundary layr. Phase averaged streamwise velocity and wall shear stress were measured by a flow sensor with a high response. Under some pulsed ingection conditions, higher velocity is observed in the region downstream of the injection hole and close to wall at the end of injection. Phase averaged wall shear stress has a peak at the end of injection. The optimum injection condition is also obtained.Furthermore, the important flow parameters of double jets are their arrangement and phase difference of injection. In common flow down arrangement with the common phase, phase averaged wall shear stress has a higher peak at the end of injection than that of single jet. As a result, such a sweep-effect of low momentum fluid near the wall by a pulsed injection is effective in the suppression of the boundary layr seperation.