Control of supersonic open jets by modified tab configurations

Abstract

The supersonic jets are not similar to subsonic jets due to the newlinepresence of shock waves. Faster decay of such jets will happen only if it newlineexploits the better momentum transfer with its still environment. Supersonic newlinejets emanating from the Convergent-Divergent nozzle consists of the newlinefollowing zones, supersonic zones of shock-cells structure, this can be sensed newlineby swaying from pitot measurement. Forthwith next zone is the characteristic newlinedecay zone, where pitot pressure measurements have a linear decrease. The newlinefinal one is the matured zone; here pitot pressure almost reaches the newlineenvironmental conditions.Control of jets can be achieved in two ways. One is newlineactive control, which imparts energy from external sources, and the second is newlinepassive control, which draws energy from the flow. The vortex generated by newlinethe active control techniques, which use an external source to generate newlinevortices azimuthally and vertically, will not travel longer distances newlinedownstream of the jets. An investigation of supersonic jet control by tabs with newlineslanted perforations was carried out for three different Mach numbers. The newlineresearch was conducted for two cases: a) tabs with constant angles and newlinedifferent perforation diameters; and b) tabs with different angles and newlineperforation diameters. Slanted perforation tabs are minor disturbances that are newlineplaced 180° apart at the exit of the nozzle. newlineExperiments were conducted for the jet Mach number of 1.8 at newlinethree Nozzle Pressure ratios (NPR). Two sets of tabs with straight and slanted newlineperforations with a constant diameter of 1mm were used. Detailed pitot newlinepressure measurements and shadowgraph images are captured to study the newlineeffect of slanted perforation in the tab. Numerical simulations for the jet Mach newlineiii newlinenumber of 1.4(NPR 5) and 1.5(NPR 3, 5.74, and 5). The Convergent- newlineDivergent model used for all the cases was having circular cross-sections. For newlinethe 1.5 jet Mach number, two sets of perforated tabs (and#934; =1.33mm, 1.65mm newlinediameter) were utilized in the control of jets. Similarly, for the 1.4 jets, four newlinesets