SUMMARY

The flows in offset diffusers of modern propulsion systems are dominated by streamwise vorticity concentrations that advect of low-momentum fluid from the flow boundaries into the core flow and give rise to flow distortion and losses at the engine inlet. Because the formation of these vortices is strongly coupled to trapped vorticity concentrations within locally-separated flow domains over concave surfaces of the diffuser bends, the present investigations exploit this coupling for controlling their evolution to significantly reduce flow distortion and losses. The strength, scale and topology of the trapped vorticity are manipulated at a throat Mach up to 0.7 using surface-mounted fluidic actuators, targeting locally-separated domains that are coupled to the streamwise vortices. The actuation alters the evolution and distribution of streamwise vortices and diminishes their strength by injection of vorticity concentrations of a prescribed sense. The proposed research focuses on elucidation and characterization of the fundamental mechanism that effects control, and on optimizing of actuation to minimize the power required for effective suppression of flow distortion and losses. It is anticipated that the proposed investigations will demonstrate the utility of trapped vorticity control for mitigating adverse effects of secondary vortices in compact inlets of propulsion systems.