Supersonic Impinging Jets
Supersonic impinging jets produce a highly unsteady flowfield leading to a noisy environment with high dynamic pressure loads on nearby surfaces. In prior work, it was demonstrated that microjet injection along the circumference of the main jet nozzle directly into the shear layer of the main jet disrupts the feedback loop inherent in high-speed impinging jet flows, thereby significantly reducing the adverse effects produced. The microjet action was due to steady blowing whose flow rate was either uniform along the circumference or varied using the eigenmode of the flow. We are developing novel closed-loop control strategies for articulating the microjet pressure is suggested, in order to maintain a uniform, reliable, and optimal reduction of these tones over the entire range of operating conditions. Experimental results from a STOVL supersonic jet facility at Mach 1.5 show that these strategies lead to 8-10 db reduction, compared to an open loop one, at the desired operating conditions. More recently, a pulsing microjet injection was used as a new control scheme to retain a uniform suppression of impinging jet noise. Through this method injection, a fairly good amount of noise reduction was achieved using 42% of the mass flow rate that led to the same level of noise reduction using steady microjet injection. As the duty cycle was increased, it was observed that the pulsed injection completely destroyed the distinct impinging tone for almost all heights. A systematic control design using these novel pulsing microjets is currently being explored.
Publications:
A.M. Annaswamy, J. Choi, D. Sahoo, F. Alvi, and H. Lou, “Active-adaptive control of acoustic resonances in supersonic impinging jets,” AIAA 2003-3565, 33 rd AIAA Fluid Dynamic Conference and Exhibit, Orlando, FL, June 2003
J. Choi, A. Annaswamy, O. Egungwu and F. Alvi , "Active Noise Control of Supersonic Impinging Jet Using Pulsed Microjets,"43rd AIAA Aerospace Sciences Meeting and Exhibit, Reno , Nevada , January 2005.
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