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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.

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The Air Force Office of Scientific Research,

The behavior of a liquid-fuel spray transversely injected into a uniform high-speed crossflow has been characterized using a laser-sheet imaging technique. The dependence of jet penetration upon jet-to-crossflow momentum ratio was studied by varying the ratio from 3 to 45. The static pressure inside the test section was varied from 14.7 to 30 psia, while the freestream Mach number was held constant at 0.4. A detailed comparison of the jet trajectories (penetration profiles) measured in this study with those predicted by currently available correlation functions revealed gross discrepancies. These discrepancies were attributed to the fact that the spray plume consists of several zones, i.e., a liquid column adjacent to the injector and ligament and droplet regions, exhibiting different characteristics which cannot be adequately described by empirical functions. A composite functional form which takes into account the behavior of these fundamcntally different spray regions has been formulated to provide a more accurate description of the penetration profile of the spray plume. The proposed empirical formula also describes the maximum (asymptotic) penetration of the spray plume in the far field. The dependence of asymptotic penetration hcight upon momentum ratio was analyzed to yield a general formula for predicting the spray trajectory over a wide range of momentum ratios. d'