SUMMARY

Internal flows subjected to adverse pressure gradients are highly susceptible to three-dimensional separation, resulting in flow instabilities and significant losses. Active flow control (AFC) effected at the flow boundary offers an attractive approach for mitigating these adverse effects by delaying separation or bypassing it altogether. The proposed investigation builds on earlier, preliminary research work that has already demonstrated the ability of fluidic-based AFC to suppress local separation within a diffuser and thereby significantly alter the cross-stream flow distribution and concomitantly the global flow characteristics leading to reduced losses and increased flow rates. The proposed investigations will focus on the interactions between the fluidic actuation jets and the cross flow with specific emphasis on elucidating the fundamental flow mechanisms that couple to and mitigate flow separation and affect its inherent dynamics in the absence of actuation. These investigations will be conducted using advanced diagnostic tools including planar and stereo particle image velocimetry and pressure sensitive paint in a new, high-quality high-speed wind tunnel facility. The proposed investigations will be conducted in collaboration with numerical simulations of the flow, and the experimental findings will be continuously compared with the results of the simulations and will aid in the development of advanced numerical turbulence models.