Axial symmetry loss of a supersonic preturbulent jet

Free underexpanded jets in a quiescent medium: A review

“…Contrary to what happens in the core of the jet, the viscous effects have here a tremendous influence, particularly because of their impact on the development of the flow instabilities and consequently on the width of the mixing layer and on the diameter of the jet. This has been formalized by [69], and confirmed by [163,152,162], who defined an initial Reynolds number Re i for the shear layer, based on the exit velocity and the distance to the Mach disk and the viscosity of the ambient fluid, such that for…”

“…increased for larger pressure ratios [143][144][145]149,121,150]; increased with the exit Mach number [149]; reduced when there occurs an enhancement of the turbulence, and so depends on the Reynolds number, which induces a rapid mixing of the high-velocity flows with the ambient fluid since we may have a thicker shear layer [144,148,[151][152][153][154]38,61].…”

Effect of the plenum-chamber diameter on the turbulent characteristics of a supersonic jet

“…In this case, it is difficult to compare the turbulent flow characteristics for different nozzles because of the necessity of controlling the roughness height. The laminar-turbulent transition occurs without violation of axial symmetry if the mean free path of the molecules in the ambient space becomes comparable with th e roughness height (5/d < 10 -3) [4]. Under these conditions, the turbulent characteristics are determined by the level of external disturbances and by the growth rates of these disturbances in the mixing layer.…”

“…The range 103 <: Re < 104 corresponds to the laminar-turbulent transition; and as the Reynolds number increases, the distance at which the transition to the turbulent regime occurs shifts from the Mach disk to the nozzle exit. Depending on the size of the nozzle-edge roughness, the transition to turbulence can follow two different scenarios [4]. If the nozzle-edge roughness is ~/d > 5-10 -3 (d is the nozzle diameter and ~ is the characteristic height of the roughness), the transition to the turbulent flow regime occurs with violation of axial symmetry of the flow in the mixing layer.…”

“…In a series of several hundred measurements, the time correlations were determined for a given delay between the laser pulses. We studied the exhaustion from a sonic nozzle 4.2 mm in diameter with the edge roughness less than 2 #m. Under these conditions, the transition to turbulence occurred without the appearance of a lobe structure at the jet boundary (the Knudsen number calculated on the basis of the mean free path in the ambient space and the roughness height was close to unity) [4]. The plenum-chamber diameter was 40 or 80 mm.…”