It is common for jets of fluid to interact with crossflow. This article reviews our understanding of the physical behavior of this important class of flow in the incompressible and compressible regimes. Experiments have significantly increased in sophistication over the past few decades, and recent experiments provide data on turbulence quantities and scalar mixing. Quantitative data at high speeds are less common, and visualization still forms an important component in estimating penetration and mixing. Simulations have progressed from the Reynolds-averaged methodology to large-eddy and hybrid methodologies. There is a general consensus on the qualitative structure of the flow at low speeds; however, the flow structure at low-velocity ratios (jet speed/crossflow speed) might be fundamentally different from the common notion of shear-layer vortices, counter-rotating vortex pairs, wakes, and horseshoe vortices. Fluid in the near field is strongly accelerated, which affects the jet trajectory, entrainment, ...

The Interaction of Jets with Crossflow

1. Introduction 2. Theoretical background 3. High temperature gas dynamics and hypersonic effects 4. Cycle analyses and energy management 5. Inlets and nozzles 6. Supersonic combustion processes and characteristics 7. Testing methods and wind-tunnels 8. Computational fluid dynamics methods and solutions for high speed reacting flows.

The Scramjet Engine: Processes and Characteristics

An experimental investigation was conducted to compare the supersonic mixing performance of a novel e ush-wall aerodynamic ramp injector with that of a physical ramp injector. The aerodynamic ramp injector consists of nine e ush-wall jets arranged to produce fuel‐ vortex interactions for mixing enhancement in a supersonic crosse ow. Test conditions included a Mach 2.0 crosse ow of air with a Reynolds number of 3.63 10 7 per meter and helium injection with jet-to-freestream momentum e ux ratios of 1.0 and 2.0. Conventional probing techniques, including species composition sampling, were employed to interrogate the e owe eld at several downstream locations. Results show that with increasing jet momentum the aeroramp exhibited a signie cant increase in fuel penetration, whereas the physical ramp showed no discernible change. The near-e eld mixing of the aeroramp was superior to that of the physical ramp; however, the physical ramp reaches a fully mixed condition at approximately half the distance of the aeroramp. As the jet momentum was increased, the far-e eld mixing performance of the aeroramp approached that of the physical ramp. In all cases the total pressure loss incurred with the aeroramp was less than that caused by the physical ramp. For both injectors the total pressure loss decreased with increasing jet momentum. It was concluded that, although physical ramps may provide better far-e eld mixing, properly designed e ush-wall injection can provide comparable mixing performance while avoiding the practical problems associated with an intrusive geometry in a scramjet combustor.

Comparison of Physical and Aerodynamic Ramps as Fuel Injectors in Supersonic Flow

The Scramjet Engine: List of Acronyms

Planar laser-induced fluorescence (PLIF) imaging has been used to examine the mixing and combustion of a sonic jet of gas injected transversely into a supersonic freestream flowing within a shock tube. Single-shot and frame-averaged fluorescence images have been acquired for nonreacting and reacting flows in side-view and end-view orientations. In the nonreacting experiments, nitric oxide seeded within the jet fluid was used to examine the penetration and mixing of the jet with the freestream, without the influence of chemical reaction and heat release. In the reacting experiments, the hydroxyl radical (OH), formed by the combustion of a hydrogen jet injected into an oxidizing freestream, was used to locate the reaction zones. The OH images indicate that combustion takes place primarily in the shear layer formed by the jet and the freestream, and in the boundary layer adjacent to the wall. For both the nonreacting and reacting results, the single-shot images show the presence of large-scale turbulent structures not apparent in the frame-averaged images. These results demonstrate the importance of examining and understanding the instantaneous flowfield, because it is the instantaneous, rather than mean state, of the flow that ultimately determines the extent to combustion.

Planar fluorescence imaging of a transverse jet in a supersonic crossflow

Experiments were conducted to determine if vortices could aid the penetration and spreading of helium in a Mach 2 a i r s t ream. A half-delta-wing injector, having a 30' semiapex angle and a 12' angle of attack, was used. This delta. configuration was de­ signed to produce leading edge vortices into which helium was injected. A flat plate of the same blockage a r e a and at the same angle of attack was also run for comparison. Measured helium concentration profiles showed that the half-delta injector was more ef­ fective than the angled flat plate in achieving greater penetration along the vortex posi­ tion. The spreading was also larger with the delta injector.

A Study of Helium Penetration and Spreading in a Mach 2 Airstream Using a Delta Wing Injector

Helium injection Mach number effect on supersonic jet penetration into Mach 2 air stream from flat plate determined from concentration measurements

Supersonic jet penetration /up to Mach 4/ into a Mach 2 airstream

Optical study of sonic and supersonic jet penetration from flat plate into Mach 2 airstream

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M. Hersch

Papers

A Study of Helium Penetration and Spreading in a Mach 2 Airstream Using a Delta Wing Injector

Supersonic jet penetration /up to Mach 4/ into a Mach 2 airstream

Optical study of sonic and supersonic jet penetration from a flat plate into a Mach 2 airstream

Experimental Method of Measuring Intensity of Turbulence in a Rocket Chamber

A schlieren technique for measuring jet penetration into a supersonic stream