Influences of semi-circular, square, and triangular grooves on mixing behavior of an axisymmetric supersonic jet

Abstract

The length of the supersonic jet ejected from the military aircraft must be reduced in order to decrease its heat signature and aeroacoustic noise and thereby to enhance its stealth capability. The reduction or manipulation of the supersonic core can be achieved through various passive control techniques. Considering this, the present study explores the mixing characteristics of supersonic jets with and without passive controls. Passive controls in the form of grooves configured at the exit of a Mach 1.73 convergent-divergent nozzle are investigated computationally. Particularly, the supersonic jet decay characteristics and flow development for a plain nozzle and a nozzle with semi-circular, square, and triangular grooves are presented. Besides, the study explores different turbulence models namely, Spalart-Allmaras, realisable k-ε, std k-ω, Shear Stress Transport (SST) k-ω and SST Transition. The realisable k-ε turbulence model is found to be the most effective one in capturing the supersonic jet structure. It is observed that the grooves produce large distortions in the jet structure, accompanied by significant mass entrainment and lateral spread. Interestingly, semi-circular grooves are proven to be most effective in all cases of expansion level than square and triangular grooves. For the semi-circular grooves, a maximum of 48.5% reduction in supersonic core length of the correctly expanded jet at Nozzle Pressure Ratio (NPR) of 5 is achieved. The reduction in supersonic core length for semi-circular grooves is 31% for the overexpanded jet at NPR 4 and 29% for the underexpanded jet at NPR7.

Comparative Analysis of Supersonic Flow in Atmospheric and Low Pressure in the Region of Shock Waves Creation for Electron Microscopy

“…For the planned experiments, the calculation state of the nozzle was determined using the theory of one-dimensional isentropic flow for the construction of this nozzle [ 42 ]. Thus, according to the dimension of the input cross-section of the nozzle—the narrowest cross-section, the so-called critical cross-section, and the output cross-section of the nozzle was determined [ 43 , 44 ].…”

An Experimental Study on the Interaction Effects between a Rectangular Supersonic Jet and a Flat Wall at Different Wall Lengths

“…Wall surface modifications alter the structure of the interacting supersonic flow significantly. For example, in passive jet control methods which employ grooves [1][2][3][4] or notches [5][6][7][8] on nozzle internal walls alter not only internal nozzle wall pressure distribution but also alter the shock structure of the emerging supersonic jet. The other type of passive control methods such as use of tabs [9][10][11], chevron configurations [12][13][14], lobes [15][16] and diagonal expansion ramps [17] for flight vehicle nozzles involve complex interaction features in the exiting supersonic flow that significantly determine the shock structure in the supersonic core, shear layer growth and its stability and also on the acoustic characteristics.…”