Abstract:
Experimental investigations of the influence of streamwise streaky structures on turbulization of a circular laminar jet are described. The qualitative characteristics of jet evolution are studied by smoke visualization of the flow pattern in the jet and by filming the transverse and longitudinal sections of the jet illuminated by the laser sheet with image stroboscopy. It is shown that the streaky structures can be generated directly at the nozzle exit, and their interaction with the Kelvin–Helmholtz ring vortices leads to emergence of azimuthal “beams” ($\Lambda$-structures) by a mechanism similar to three-dimensional distortion of the two-dimensional Tollmien–Schlichting wave at the nonlinear stage of the classical transition in near-wall flows. The effect of the jet-exhaustion velocity and acoustic action on jet turbulization is considered.
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