【摘 要】
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This paper reports an experimental study on the supersonic jet surface flow structure visualization and shear stress field measurement issuing from a rectangular nozzle with extended shelf.The evolution of the near-field surface flow structures with an in
【机 构】
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College of Aerospace Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,C
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This paper reports an experimental study on the supersonic jet surface flow structure visualization and shear stress field measurement issuing from a rectangular nozzle with extended shelf.The evolution of the near-field surface flow structures with an increased Nozzle Pressure Ratio (NPR) is successfully captured by the surface oil flow,infrared detection technology,and the Shear-Sensitive Liquid Crystal Coating (SSLCC) technique.Results reveal that under smaller NPR,the wall flow structure is similar to that of a jet without the extended shelf i.e.,clean jets,and this is caused by insufficient effect on the boundary layer.However,at higher amplitudes of NPR,there exists a significant effect of the boundary layer,as a near triangular separation forms on the trailing edge of the Mach stem due to the adverse pressure gradient,which is visualized for the very first time in this paper.Furthermore,the vector field of shear stress is measured quan-titatively by SSLCC technique.Results shows that the magnitude of shear stress heightened with NPR increasing,and the directions of shear stress changes across the shock wave and expansion fans.In addition,surface streamlines measured by SSLCC is significantly consistent with the streamlines visualized using the oil flow technique.
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