On the origins of transverse jet shear layer instability transition

Effect of tabs on transverse jet instabilities, structure, vorticity dynamics and mixing

“…This overall behaviour in figure 12( a ) was not unexpected given that the USL is naturally AU at for this jet mixture (Shoji et al. 2020 b ), and growth of asymmetries is shown to be suppressed by the larger dominant axisymmetric USL instability mode (Alves et al. 2007; Regan & Mahesh 2017), resulting in symmetric CVP structures at low values (Getsinger et al.…”

“…More recently, Shoji et al. (2020 b ) observed that even very small changes in the jet constituent species, causing a change in the bulk viscosity of the jet mixture, for example, due to the presence of acetone, can alter this transition point if other non-dimensional parameters such as , and remain fixed. Such changes in the jet-to-crossflow viscosity ratio require small changes to the mean jet velocity, and as a result alter the jet momentum thickness at the nozzle exit, which is noted by Megerian et al.…”

“…For an equidensity flush nozzle-injected jet with a jet Reynolds number of and an acetone mole fraction of , the critical transition from convective to absolute instability takes place at (Shoji et al. 2020 b ). Representative spectral contour plots for hotwire data taken along the USL for the transverse jet with the original fifth-order polynomial nozzle are shown in figure 5( a ) for the case of an AU USL at , and in figure 6( a ) for the case of a CU USL for .…”

“…Only had an USL which was clearly CU in the absence of a tab (Shoji et al. 2020 b ). The non-tabbed mode structures over the momentum flux ratio range in question (figures 17 a –19 a ) agreed quite well with the dynamics seen in the snapshot POD for the flush nozzle-injected JICF for the same range by Gevorkyan et al.…”

“…When considering the instability characteristics of the USL, the frequency content () can be non-dimensionalized using a Strouhal number, , based on the jet diameter; relevant Strouhal numbers can also be defined in terms of the jet's upstream momentum thickness () (Shoji et al. 2020 b ).

Figure 1.( a ) Schematic of a flush round jet injected normally into crossflow, with representative depictions of the relevant vortical structures.

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