DOI: 10.36347/sjet.2019.v07i11.006

Pages: 311-326

The results of a Mach 1.5 elliptical jet issuing from a convergent divergent elliptical nozzle of aspect ratio 3, controlled with two triangular tabs of 2.5% blockage each are presented. The decay for the jets with tabs located at the extremities of the major and minor axes are compared for different nozzle pressure ratio NPR 3, 4, 5, and 6. The decay of the uncontrolled jet and without tabs is also included for comparison. It is seen that among the tab orientations, placing along the minor tabs along minor axis is found to be the best mixing promoter resulting in 80% and 74% core length reduction, respectively, at NPR 3 and NPR 4. At NPR 6, the ventilated triangular tabs with circular holes on major axis and triangular tabs with triangular holes on minor axis are found to be more effective in enhancing the mixing. The triangular tabs used in present study is special in the sense that it is capable of producing mixing promoting vortices of continuously varying size, in accordance with the vortex theory, unlike conventional rectangular tabs which will shed mixing promoting vortices of uniform size only. For all the cases, tabs along minor axis promotes mixing and tabs along major axis retard the mixing. Among the ventilations studied, the circular hole is found to be superior to the triangular hole. This superiority of circular ventilation is found to be independent of the expansion level at the nozzle exit.