A novel control of flow separation by shooting vortex rings at the separated shear layer of a thin airfoil is presented in this paper. A vortex generator was attached to the wall of the test section of a wind tunnel parallel to the main flow at a position upstream to the thin airfoil with the large separation. Thus, vortex rings moved in the main flow and then collided on the separated shear layer of the thin airfoil. This paper shows the effect of the addition of momentum by vortex rings on the mitigation of separation. The phase averaged flow field was observed by a flow visualization and velocity measurement to investigate how the vortex ring mitigates a separated shear layer. The large vortex structure was formed near the leading edge by the interaction between the vortex ring and separated shear layer. The separated shear layer reattaches at this position, and the separation bubble is formed. This means that the separation is suppressed locally by the vortex ring at this phase. The effect of the vortex ring on the suppression of separation was evaluated by the momentum defect of the wake measured at the downstream position. The amount of momentum given by the vortex rings in a unit time increases with increasing the frequency if the momentum of each vortex ring is fixed. The multi orifice aligned in the spanwise direction were tested to suppress separation 'uniformly in the spanwise direction.
展开▼
