Abstract
This work explores the extent of jet mixing for a supersonic jet coming out of a Mach 1.8 convergent-divergent nozzle, controlled with two short rectangular vortex-generating actuators located diametrically opposite to each other with an emphasis on numerical methodology. The blockage ratio offered by the tabs is around 0.05. The numerical investigations were carried out by using a commercial computational fluid dynamics (CFD) package and all the simulations were performed by employing steady Reynolds-averaged Navier–Stokes equations and shear-stress transport k−ω turbulence model on a three-dimensional computational space for more accuracy. The numerical calculations are administered at nozzle pressure ratios (NPRs) of 4, 5, 6, 7 and 8, covering the overexpanded, the correctly expanded and the underexpanded conditions. The centerline pressure decay and the pressure profiles are plotted for both uncontrolled and the controlled jets. Numerical schlieren images are used to capture the barrel shock, the expansion fans and the Mach waves present in the flow field. Mach contours are also delineated at varying NPRs indicating the number of shock cells, their length and the variation of the shock cell structure and strength, to substantiate the prominent findings. The outcomes of this research are observed to be in sensible concurrence with the demonstrated exploratory findings. A reduction in the jet core length of 75% is attained with small vortex-generating actuators, compared to an uncontrolled jet, corresponding to nozzle pressure ratio 5. It was also seen that the controlled jet gets bifurcated downstream of the nozzle exit at a distance of about 5 D, where D is the nozzle exit diameter. Furthermore, it was fascinating to observe that the jet spread increases downstream of the nozzle exit for the controlled jet, as compared to the uncontrolled jet at any given NPR.
Highlights
The challenge of supersonic jet flow exhibiting augmented mixing is relevant in numerous technological applications, has been an area of multitudinous research for several years and remains a contemporary topic
Recalling our concept of vortex dynamics, it is understood that large scale vortical structures are efficient suction creators and have a shorter life span and for the system to be in agreement with the law of conservation of momentum, these large-scale vortices, known as entertainers, get tattered into smaller eddies
Supersonic flow is largely subdued by waves, and precise measurement of actual total pressure and Mach number at every spatial position in the direction of nozzle exit is difficult, experimentally or numerically
Summary
The challenge of supersonic jet flow exhibiting augmented mixing is relevant in numerous technological applications, has been an area of multitudinous research for several years and remains a contemporary topic. A recent work by Thillaikumar et al (2020) suggested that the introduction of vortex actuating tabs in the divergent section of the supersonic nozzle changes the structure of the shock cell, thereby reducing the jet core length [10]. From the literature it is established that symmetricity leads to rapid the jet literature, it is i.e., established tabs are ineffective opposite in the overexpanded in case of under development, two tabsthat placed diametrically to each otherflow willbut cause complete jet expanded tab length a profound impact in enhancing jet mixing compared to tab for bifurcation.flow, thishas configuration was chosen such that the blockage offered bywidth the tabs same projected area.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
