Abstract
In order to establish the active control system by using the vortex generator jets (VGJs), it is necessary to understand the detailed suppression mechanism of the flow separation in the diffuser. An opening angle of the diffuser can be changed from 8 to 15 deg corresponding to three flow regimes, "Unstalled", "Appreciable Stall" and "Transitory Stall". A micro wall flow sensor was used for measurement of forward flow fraction. It is found that VGJ makes the local forward flow fraction increase and prevents the stall. Although the effect of separation control is obtained resulting from the higher jet velocity ratio, excessive jet velocity ratio introduces pressure loss due to the lower diffuser effectiveness.
