Control of Vorticity Generation in an Acoustically Excited Jet in Crossflow

Karagozian, Ann; Megerian, Sevan; Alves, Leonardo Santos de Brito; George, Marcus; Kelly, R. E.

doi:10.2514/6.2005-303

Cited by 7 publications

(1 citation statement)

References 29 publications

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“…Experimental measurements of the dominant St in the shear layer have varied widely, on the other hand. Karagozian et al (2005) report a dominant St of 0.8 for r = 7 and r = 8 (matching our r = 7 result exactly), but a jump to higher frequencies (St ≈ 1.0-1.1) for r = 5 and lower. Recent work by Karagozian et al suggests that in addition to the velocity ratio, a host of other factors, e.g.…”

Section: Vorticity Isosurfacessupporting

confidence: 87%

Vorticity structure and evolution in a transverse jet

Marzouk

Ghoniem

2007

J. Fluid Mech.

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Transverse jets arise in many applications, including propulsion, effluent dispersion, oil field flows, and V/STOL aerodynamics. This study seeks a fundamental, mechanistic understanding of the structure and evolution of vorticity in the transverse jet. We develop a high-resolution three-dimensional vortex simulation of the transverse jet at large Reynolds number and consider jet-to-crossflow velocity ratiosrranging from 5 to 10. A new formulation of vorticity-flux boundary conditions accounts for the interaction of channel wall vorticity with the jet flow immediately around the orifice. We demonstrate that the nascent jet shear layer contains not only azimuthal vorticity generated in the jet pipe, but wall-normal and azimuthal perturbations resulting from the jet–crossflow interaction. This formulation also yields analytical expressions for vortex lines in the near field as a function ofr.Transformation of the cylindrical shear layer emanating from the orifice begins with axial elongation of its lee side to form sections of counter-rotating vorticity aligned with the jet trajectory. Periodic roll-up of the shear layer accompanies this deformation, creating complementary vortex arcs on the lee and windward sides of the jet. Counter-rotating vorticity then drives lee-side roll-ups in the windward direction, along the normal to the jet trajectory. Azimuthal vortex arcs of alternating sign thus approach each other on the windward boundary of the jet. Accordingly, initially planar material rings on the shear layer fold completely and assume an interlocking structure that persists for several diameters above the jet exit. Though the near field of the jet is dominated by deformation and periodic roll-up of the shear layer, the resulting counter-rotating vorticity is a pronounced feature of the mean field; in turn, the mean counter-rotation exerts a substantial influence on the deformation of the shear layer. Following the pronounced bending of the trajectory into the crossflow, we observe a sudden breakdown of near-field vortical structures into a dense distribution of smaller scales. Spatial filtering of this region reveals the persistence of counter-rotating streamwise vorticity initiated in the near field.

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Section: Vorticity Isosurfacessupporting

confidence: 87%

Vorticity structure and evolution in a transverse jet

Marzouk

Ghoniem

2007

J. Fluid Mech.

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Controlling particle dispersion in a transverse jet by synchronized injection

Campolo¹,

Cremese²,

Soldati³

2008

AIChE Journal

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The dispersion produced by a jet injecting nil. croparticics (or droplets) in a cross stream is controiled by the interaction between injected species and large scale flow structures characteristic of the jet in crossflow system. In a previous work we characterized accurately the dynamics of the particles undergoing dispersion under the action of the shear layer vortices (SLV) which form in the jet shear layer. In this article, we prol)ose a strate, y to control and possibly optimize the dispersion of species injected in the cross stream. This strategy is based on injecting particle packets (or puffs) synchronized with the time of formation of the shear layer vortices. The possibility to increase or decrease particle dissersion by synchronized, pulsed injection is explored by identifying the relevant parameters of the particle/flow, system; the effictiveness of this strategy is verified by exploring a representative sample of the parameter range

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