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Characteristics of Parallel and Inward Canted Sonic Twinjets

R. Mohana Murali(1), S. M. Aravindh Kumar(2), Ethirajan Rathakrishnan(3*)

(1) Department of Aerospace Engineering, Indian Institute of Technology Kanpur, India
(2) Department of Aerospace Engineering, SRM Institute of Science and Technology, India
(3) Department of Aerospace Engineering, Indian Institute of Technology, India
(*) Corresponding author



Twin unventilated sonic jets of parallel and inward canting configurations with non-dimensional inter-nozzle spacing of 3, 4 and 5 were studied experimentally at different levels of underexpansion corresponding to nozzle pressure ratio (NPR) of 3, 5 and 7. The results of measured pitot pressure distribution show that, for parallel twinjet with inter-nozzle spacing of 4 and 5, the merging point shifts downstream with increase of NPR, whereas for inter-nozzle spacing of 3, the merging point moves upstream with increasing NPR. For inward canted twinjet, the merging point shifted upstream compared to parallel twinjet at all the NPRs and inter-nozzle spacings studied. The shifting of merging point and the maximum centerline pressure level are strongly influenced by inter-nozzle spacing. For inter-nozzle spacing of 3, the inward canted twinjet confluences completely at about 20 diameters, whereas the parallel twinjet confluences only around 30 diameters. With increase of inter-nozzle spacing from 3 to 5, the confluence is slightly delayed for both the twinjets. The shadowgraph pictures confirmed the presence of Mach disk at NPRs 5 and 7 for all the twinjet configurations.
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Twinjets; Inward Canted; Nozzle Pressure Ratio; Inter-Nozzle Spacing; Shock-Cells

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