A three-dimensional numerical investigation on drag reduction of a supersonic spherical body with an opposing jet

Abstract

A three-dimensional numerical simulation of a supersonic free-stream at Mach 2.5 over a spherical body with a sonic opposing jet from its stagnation point is carried out by solving the three-dimensional Navier-Stokes equations coupled with the standard k-" turbulence model. It is aimed to investigate the effects of the jet on the drag reduction on the body and the flow field around the body. The influences of the jet pressure, the nozzle size of the jet, and the angle of attack are systematically studied for the purpose. An unsteady oscillatory motion mode and a nearly steady motion mode are identified depending upon the jet total pressure. There exists a critical jet pressure where the flow mode transition from one to the other happens suddenly and this critical pressure value varies approximately linearly with the jet nozzle exit size inversely. For the zero angle of attack, the results show that there exists a maximum overall drag reduction as the jet pressure changes for each jet nozzle size and the maximum overall drag reduction always happens at the unsteady oscillatory motion mode. The main shock in front of the body is pushed backward by the jet and the displacement of the shock decreases with the increase of the angle of attack, and the drag reduction efficiency also decreases with the angle. Regarding to the mode transition, it is found that the drag rises suddenly when the transition happens for the angle of attack smaller than or equal to 5 but it does not result in the rise for the angle larger than 5 . The results show that the maximum overall drag reduction can be reached as high as 32.6% for the cases studied. The present results provide useful information for drag reduction applications using an opposing jet.

Forebody shock control devices for drag and aero-heating reduction: A comprehensive survey with a practical perspective

“…More importantly, slightly beyond the critical value of pressure ratio, a bifurcation phenomenon where transition from one mode to the other and back takes place [136,147]. This is associated with an abrupt rise in drag that continues to fall with a lower slope afterwards [136,140,151]. This drag jump becomes more severe if the jet exit Mach number of orifice are increase [152].…”

“…For non-lifting vehicles, opposing jets increase the lift and the lift-to-drag ratio of the vehicles at incidence [153,154]. It has also been shown that at incidence, the jump between LPM and SMP becomes less severe [151].…”

“…At the critical pressure ratio, the jet length and the drag reduction reach their maximum values. The value of the critical pressure ratio is dependent on the forebody configuration, jet Mach value, and orifice area [140,151]. As the Mach number and orifice area increase, both the critical pressure ratio and the associated maximum drag reduction decrease [152].…”

“…All numerical simulation studies adopted the 2D axisymmetric computational domains. Half 3D domains were used in case of nonzero incidences [151,153,155,156] or in cases if the vehicle is not axisymmetric [154,197,198]. The three-dimensionality of opposing jet flow from an axisymmetric body at zero incidence was first investigated by Chen et al [181] in their high quality numerical study.…”

Influence of angle of attack on a combined opposing jet and platelet transpiration cooling blunt nose in hypersonic vehicle

“…Consequently, the thermal protection performance between windward and leeward sides can have different properties. Zhou and Ji (2014) investigated the flow structure of unsteady oscillatory motion mode with an angle of attack in an opposing jet flow, showing that the shock stand-off distance is significantly shortened with increased angle of attack, and the reattachment shock wave on the windward side moves upstream. Daso et al (2009) tested the 2.6%-scale Apollo capsule model in a wind tunnel of supersonic freestream showing that thermal protection decreases with increased angle of attack, but the opposing jet still cools vehicles even at a 9° angle of attack.…”