Detailed flow physics of the supersonic jet interaction flow field

Abstract

The supersonic jet interaction flow field generated by a sonic circular jet with a pressure ratio of 532 exhausting into a turbulent MACH 4.0 cross flow over a flat plate was investigated using numerical simulations. The simulations made use of the three-dimensional Reynolds-averaged Navier-Stokes ͑RANS͒ equations coupled with Wilcox's 1998 k-turbulence model. The numerical solution was validated with experimental data that include the pressure distribution on the flat plate, with an empirical formula for the height of the barrel shock, and with the Schlieren pictures showing the location and shape of the main shock formations. The simulations correctly captured the location and shape of the main flow features and compared favorably with the experimental pressure distribution on the flat plate. The validated numerical simulation was used to investigate in detail the flow physics. The flow field was found to be dominated by the shock formations and their coupling with the strong vortical structures. Three primary shock formations were observed: a barrel shock, a bow shock, and a separation-induced shock wave. While the general structure of the barrel shock was found to be similar to that of the underexpanded jet exhausting into a quiescent medium, two unique features distinguished the flow field: the concave indentation in the leeside of the recompression ͑barrel͒ shock and the folding of the windward side of the barrel shock due to an inner reflection line. The presence of the steep pressure gradients associated with the shocks creates strong vortical motions in the fluid. Six primary vortices were identified: ͑i͒ the well-known horseshoe vortex, ͑ii͒ an upper trailing vortex, ͑iii͒ two trailing vortices formed in the separation region and, aft of the bow shock wave, ͑iv͒ two more trailing vortices that eventually merge together into one single rotational motion. The low-pressure region aft of the injector was found to be generated by the combined effect of the concave indentation in the leeside of the barrel shock and the lower trailing vortices. The trailing vortices were found to be the main mechanism responsible for the mixing of the injectant with the freestream fluid.

Transient interaction between a reaction control jet and a hypersonic crossflow

“…In a supersonic crossflow, Viti et al [14] observed horseshoe vortex behaviour similar to that of a subsonic crossflow. Fluid from the re-circulation region with vorticity the opposite sign to the wall boundary layer was transported from the wall and deposited behind the jet to form part of the counter-rotating vortex pair, while fluid from vortices with the same sign as the wall boundary layer travelled downstream along the plate.…”

“…These three vortices rotate with respect to each other around a common longitudinal axis. While the existence of these vortices has been reported [14], their unsteady motion has not been detailed. As these vortices dominate the far-field, their unsteady motion is likely to have a significant influence on the interaction force.…”

“…In this region the time-averaged velocity field is dominated by a single streamwise-oriented counter-rotating vortex pair [10]. The single counter-rotating vortex pair observed in the time-averaged flow emerges from the merging of three smaller longitudinal trailing vortices [14]; two vortices are developed by contact between the slow jet fluid downstream of the Mach disk and the fast freestream, the other originates on the windward side of the barrel shock. These three vortices rotate with respect to each other around a common longitudinal axis.…”

“…Kawai et al [16] also identified a set of counter-rotating vortices inside the boundary layer in the wake region, and proposed that these were induced by suction from the counter-rotating vortex pair. Viti et al [14] contend that these vortices originate in the re-circulation region immediately upstream of the jet outlet. Viti et al [14] also found that, in a Mach 4 crossflow, there is an upper set of counter-rotating vortices, that follow the leading edge of the bow shock away from the plate.…”

“…As these vortices dominate the far-field, their unsteady motion is likely to have a significant influence on the interaction force. Other longitudinal vortices have been identified [9,14,16], the structure of which depends on freestream Mach number.…”