ACTIVE SEPARATION CONTROL WITH LONGITUDINAL VORTICES GENERATED BY THREE TYPES OF JET ORIFICE SHAPE

摘要

In order to suppress the separation, the fluid particles which have large energy of the freestream are supplied to decelerated fluid particles in the boundary layer by longitudinal vortices. Jets issuing through small holes in a wall into the freestream have proven effective in the control of boundary layer separation. The vortex generator jets can adjust the strength of longitudinal vortices by varying the jet speed. Furthermore, for flow situations where separation control is not needed, parasitic drag can be avoided with the jet flow turned off. The vortex generator jet method is active control of flow separation that has the ability to provide a time-varying control action to optimize performance under a wide range of flow conditions. In this study, the suppression effect of the jet orifice shape with non-circular orifices is investigated to make more effective the active separation control system. The vortex generator jets with three types of jet orifice (circular, triangular and square orifices) were used in the separation control of a two dimensional diffuser. The triangular orifice makes strong the vorticity of longitudinal vortices and effective the pressure recovery in the diffuser in comparison with the other orifice shapes.