Manipulation of Streamwise Vorticity in an Emulated Diffuser Boundary Layer Using Hybrid Flow Control

The formation and interaction of streamwise vorticity generated by surface-mounted passive (micro-vanes) and active (synthetic jets) flow control elements is investigated experimentally in a small-scale wind tunnel at high subsonic speeds (M < 0.6). Streamwise vortices are generated within the boundary layer of a converging-diverging wall insert that is designed to provide an adverse pressure gradient similar to the pressure gradient within a typical offset diffuser. Hybrid actuation is demonstrated by combining the micro-vanes with synthetic jets in tandem or by integrating the jets into vanes. Tandem actuation is accomplished using synthetic jet actuators that are yawed to match the vanes’ yaw angle and skewed to generate streamwise vortices of matching sense. Both approaches lead to augmentation of the primary vanes’ vortices and enhance their pairing. These approaches provide “fail-safe” control devices having robust nominal control effectiveness by the vane elements coupled with enhancement by the jets.