Efficacy of Delta-Tab in Controlling the Mixing Characteristics of Mach 1.8 Jet

Abstract

This present investigation inspects the mixing promoting the efficacy of two short delta tabs which is axis-symmetric, mounted circumferentially antipodal at the end for a Mach number 1.8 convergent-divergent circular nozzle computationally with the nozzle pressure ratios (NPRs) ranging from 4 to 8 with a unit step of one that covers all the critical states of the jet i.e., the overexpanded, the correctly-expanded and the underexpanded states of the jet. In order to minimize thrust loss, the geometric blockage offered by each delta tab is kept within 2.5%. The computational assessment is conducted by adopting and employing ANSYS-FLUENT which is a comprehensive engineering simulation software. Further, the entire steady flow computations are carried out on a three-dimensional numerical enclosure by implementing Reynolds-averaged Navier-Stokes equations along with the κ-omega shear stress transport turbulence model. Interestingly, vital plots including the centerline pressure decay as well as the pressure profiles are depicted for uncontrolled and controlled jets accordingly. Also, numerically obtained schlieren illustrations are adopted for visualization of the shock cell structure, expansion fan, and the Mach wave structure existing in the stream field. Furthermore, Mach variations are also depicted for the varied nozzle pressure ratios in the form of contours. The shock-strength, shock-length, and the progressive disparity found in the shock structures are reasonably demonstrated by the Mach contours. The results of this research are discovered to be in sensible concurrence with the earlier established exploratory results. A maximum core length reduction of 70.81% is observed in underexpanded condition at the nozzle pressure ratio of 6. Absorbingly, a controlled jet has been seen to get split in equal proportion along the succeeding direction of the nozzle exit at a distance of approximately 5De, De indicating the exit diameter of the nozzle. Moreover, it was appealing to detect the development of jet dispersion along the succeeding direction of the nozzle exit periphery. The short delta tabs also performed satisfactorily in diminishing the waves and reducing the shock cell length as depicted via numerical schlieren images.

Keywords

• centerline pressure decay; jet mixing; core length; mach contours; numerical schlieren; rans; mach number.