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Free underexpanded jets in a quiescent medium: A review

“…This is certainly the most studied feature in the literature, be it experimentally [12,30,35,40,43,49,51,[56][57][58][59]62,64,, theoretically [13,29,67,76,78,[95][96][97][98][99][100][101][102][103][104][105][106][107][108][109] or numerically [14,20,22,34,41,59,63,75,81,82,84,91,[110][111][112][113][114][115][...…”

“…Among the huge amount of studies, it appears that the Mach disk location is mainly governed by the pressure ratio [29,30,62,[67][68][69][70]72,[74][75][76][124][125][126][127][128][129]12,57,78,64,81,43,105,[83][84][85][86][87]121,[89][90][91][92]109 independent of the fluid [67,74,78,83,43]; not clearly influenced by the exit nozzle angle since some studies show no noticeable effects [62,[68][69][70]74,78] while others present some influence [29,56,30,126,…”

“…If we now consider the measurements expressed in function of η e [29,56,30,68,69,72,75,76,126,125,12,57,78,82,83,43,105,129,121,89,91], the behavior of the position is now less clear, as shown in Fig. 9.…”

“…This feature is also poorly documented and there are still few papers that give some insights on this characteristic length, be it experimentally [56,30,75,64,43,91], theoretically [101,142,46,47,7] or numerically [75,112,119,91]. The main reason is certainly the various issues raised by its observation.…”

“…it increases with the pressure ratio [30,75,64,43,47,121]; it increases with the exit Mach number [30,43,46,121]; it depends on the geometry of the nozzle [56,30,43,51].…”