BOUNDARY LAYER SEPARATION CONTROL USING VORTEX GENERATOR JETS

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Jets issuing through small holes in a wall into a freestream have proven effective in the control of boundary layer separation. Longitudinal vortices are produced by the interaction between the jets and the freestream. The mechanism for suppressing flow separation was studied experimentally by making a comparison between the effect of steady jets and that of pulsed jets on generating longitudinal vortices. The effect of the jet pitch angle and jet to freestream velocity ratio on suppressing flow separation was studied. Secondary flow fields at several downstream locations were measured to know the behavior of longitudinal vortices. The most important results for attaining the suppression of separation control are that not only the vortices are strong but also they continue to be near the wall.Vortex generator jets can be adapted for various flow changes. This is an advantageous characteristic compared with the case of solid vortex generator. An active separation control feedback system was developed based on the knowledge on the separation control mechanism. The system has been actually applied to several flow conditions and has been confirmed to be useful.