Compressibility effects in supersonic transverse injection flowfields

Abstract

The flowfields created by transverse injection of sonic gaseous jets through a circular nozzle into a supersonic crossflow have been experimentally investigated using planar Rayleigh/Mie scattering from silicon dioxide particles seeded into the crossflow stream. Helium and air were used as injectant gases allowing an examination of the effects of compressibility on the large-scale structural development and near-field mixing characteristics present within the flowfield. Instantaneous images from end and side view image planes show a highly three-dimensional interaction dominated by both large-and small-scale vortices. Analyses of these image ensembles provide jet spreading and penetration characteristics, standard deviation statistics, large-scale mixing information, and two-dimensional spatial correlation fields. Results indicate that injectant molecular weight variations do not strongly affect the jet's transverse penetration into the crossflow, although they lead to substantially different compressibility levels that dramatically influence the characteristics of the large-scale structures formed in the shear layer and the entrainment and mixing occurring between the injectant and crossflow fluids. The large-scale eddies tend to rapidly break-up in the low compressibility injection case while those in the high compressibility case remain coherent over a longer spatial range. Mixing layer fluctuations present in the low compressibility case intrude deeply into the jet fluid as compared to the high compressibility case, where these fluctuations are confined near the jet edge.

Experimental Studies of Pylon-Aided Fuel Injection into a Supersonic Crossflow

“…6), the jet plume exhibits the familiar behavior observed in previous research [24,25]. At the jet injection location (x=d 0), the plume is mostly concentrated near the floor.…”

Hybrid LES/RANS Simulation of Transverse Sonic Injection into a Mach 2 Flow

“…Tam, et al [13] used the Menter-BSL and Menter-SST [14] RANS models as well as the k-ω model of Wilcox [15] to simulate the sonic injection experiments of Gruber, et al [9][10][11][12]. It was shown that the BSL model and the Wilcox model provided the best agreement with the surface pressure measurements of Gruber.…”

“…They were able to obtain acceptable results by forcing the inflow boundary layer using a population of hairpin-type vortices generated through a separate calculation. In the present work, a hybrid LES/RANS method [20][21][22][23] is used to simulate the experiments of Gruber and co-workers [9][10][11][12], which involve the injection of sonic air or helium into a Mach 1.98 air cross-flow. This study is part of a continuing effort to develop hybrid LES/RANS strategies that are more suited for computing strongly-interacting, threedimensional wall-bounded flows encountered in high-speed engine concepts.…”

“…Optical methods allowed researchers to discern the major flow phenomena shown in this figure such as the prominent bow shock, Mach disk in the interior of the injection plume, counter-rotating vortices in the injection plume, and the wake and vortex regions beneath the injection plume. More recent studies [7][8][9][10][11][12] utilized laser-tracking technology in addition to optical techniques to glean more information from wind tunnel tests. Even with newer technology, quantitative results are often limited.…”

Hybrid LES of Detonations in Reacting Multi-Phase Mixtures

“…Finally, vertical wake vortices form between the wall boundary layer and the jet plume, downstream of the injection. Their contribution to the mixing process is uncertain (Gruber et al [1997]). Although simple from a conceptual point of view, it can be inferred from the above observations that this injection methodology leads to a rather complex flow pattern.…”