Aspect Ratio Effect on Mach 1.5 Rectangular Jet Mixing

An experimental investigation on the mixing characteristics of Mach 1.5 rectangular jet emanating from aspect ratios (<italic>AR</italic>s) 2 and 3 convergent-divergent nozzles is carried out at nozzle pressure ratios (<italic>NPR</italic>s) 3, 3.69, 4 and 5, respectively. At overexpanded (<italic>NPR</italic>3), correctly expanded (<italic>NPR</italic> 3.69) and underexpanded (<italic>NPR</italic>s 4, 5) levels of Mach 1.5 jet, the Pitot pressure measured along the centerline of <italic>AR</italic>2 and <italic>AR</italic>3 rectangular jets showed that the influence of aspect ratio on the jet mixing is not as strong as expected. The effect of aspect ratio is noticeable only in the core of both the jets. The core length of <italic>AR</italic>2 jet is shorter than <italic>AR</italic>3 jet at all the <italic>NPR</italic>s, which indicates faster mixing of <italic>AR</italic>2 jet with ambient fluid as compared to <italic>AR</italic>3 jet. But after core, the decay of <italic>AR</italic>2 and <italic>AR</italic>3 jets in the characteristic decay region remained almost same at all the <italic>NPR</italic>s except at correctly expanded <italic>NPR</italic> of 3.69, the <italic>AR</italic>3 jet decays slightly faster than <italic>AR</italic>2 jet. For all the cases, the jets have become fully developed together at far downstream location. The pressure profiles taken along major axis and minor axis of Mach 1.5 rectangular jets confirm the faster spreading of <italic>AR</italic>2 and <italic>AR</italic>3 jets along minor axis than along major axis. Both the jets are found to switch axes between <inline-formula> <tex-math notation="LaTeX">$8D_{e}$ </tex-math></inline-formula> to <inline-formula> <tex-math notation="LaTeX">$10D_{e}$ </tex-math></inline-formula>. The shadowgraph visualization reveals the complex structure of waves present in the major axis and minor axis planes of <italic>AR</italic>2 and <italic>AR</italic>3 rectangular jets.

Abstract licence: CC BY-NC-ND

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