Experimental study of transonic jet based on Tomo-PIV and Tomo-BOS

This study experimentally investigates complex wave structures and flow characteristics in a transonic free jet using two high-resolution optical diagnostics techniques: tomographic particle image velocimetry (Tomo-PIV) and tomographic background oriented schlieren (Tomo-BOS). The measurements reveal three typical flow features in the jet: the potential core, shock cells, and shear layers. Notably, the shear layer displays significant velocity gradient variations across the lip line and plays a critical role in pressure regulation. The first invariant of the velocity gradient tensor, P, effectively characterizes local compressibility effects, facilitating the identification of key flow structures. In conjunction with −Qs analysis, the results emphasize shear-driven deformation and the radial decay of wave intensity. Overall, the study demonstrates that current experimental techniques enable preliminary quantitative evaluation of transonic wave phenomena, providing valuable tools for the analysis of compressible flows.