Controlling sonic rectangular jet with nozzle trailing edge modification

Sonic rectangular jet emanating from a convergent nozzle of aspect ratio 2 with modified trailing edge in the form of triangular extension on its widest side is investigated experimentally at different nozzle pressure ratios corresponding to underexpanded states of sonic jet. To assess the impact of trailing edge modification on jet mixing, the sonic rectangular jet from aspect ratio two plain convergent nozzle (without trailing edge modification) is also studied. The centerline pressure decay results at nozzle pressure ratios 2, 3, 4 and 5 confirm the superiority of modified jet (jet from trailing edge modified nozzle) over plain jet from the mixing point of view. At all the pressure ratios, the modified jet possessed shorter core and weaker shock and expansion waves compared to plain jet, which is an outcome of faster mixing of modified jet with ambient fluid. The enhanced mixing caused the modified jet to decay faster than the plain jet. An appreciable core length reduction of about 32% is noticed at pressure ratio of 5. The modified jet experienced increased spread along major axis than along minor axis owing to the restriction offered by the triangular extension on jet spread along minor axis. Thus, the axis switching was absent in modified jet compared to plain jet switching axes at all pressure ratios. The shadowgraph images confirmed the presence of weaker waves in the modified jet. Also, the images confirmed the absence of Mach disk in the modified jet at pressure ratio of 5 compared to plain jet.