Optimization of Controlled Jets in Crossflow

Shapiro, Stephen R.; King, Jonathan; M’Closkey, Robert T.; Karagozian, Ann

doi:10.2514/1.19457

Cited by 81 publications

(59 citation statements)

References 19 publications

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“…Thus there is no strong coupling between these two phenomena. This observation is consistent with the fact that the Strouhal number of the wake vortices (reported for example by Fric & Roshko 1994) is different from that of the jet shear-layer vortices reported by Shapiro et al (2006). Modes 4 and 5 in figure 4 show that the jet shear-layer vortices form along the jet trajectory about one jet diameter downstream from the the jet exit.…”

Section: Mean Velocities and Pod Modessupporting

confidence: 91%

A turbulent jet in crossflow analysed with proper orthogonal decomposition

2007

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Detailed instantaneous velocity fields of a jet in crossflow have been measured with stereoscopic particle image velocimetry (PIV). The jet originated from a fully developed turbulent pipe flow and entered a crossflow with a turbulent boundary layer. The Reynolds number based on crossflow velocity and pipe diameter was 2400 and the jet to crossflow velocity ratios wereR=3.3 andR=1.3. The experimental data have been analysed by proper orthogonal decomposition (POD). ForR=3.3, the results in several different planes indicate that the wake vortices are the dominant dynamic flow structures and that they interact strongly with the jet core. The analysis identifies jet shear-layer vortices and finds that these vortical structures are more local and thus less dominant. ForR=1.3, on the other hand, jet shear-layer vortices are the most dominant, while the wake vortices are much less important. For both cases, the analysis finds that the shear-layer vortices are not coupled to the dynamics of the wake vortices. Finally, the hanging vortices are identified and their contribution to the counter-rotating vortex pair (CVP) and interaction with the newly created wake vortices are described.

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Section: Mean Velocities and Pod Modessupporting

confidence: 91%

A turbulent jet in crossflow analysed with proper orthogonal decomposition

2007

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“…This mean flow structure appears to lie somewhere between that of the continuous and non-actuated flows, but only after a sufficient downstream flow development (see Figs. 20,21,22,23,24,25,26,27,28,and 29). …”

Section: Far-field Flow Structurementioning

confidence: 98%

“…However, Johari and Mc Manus [13] showed that jet penetration can depend on the jet pulsation frequency. Shapiro et al [26] found that during acoustic forcing of a continuous jet in crossflow, certain forcing frequencies caused an interaction between the vortices from successive jet pulses therefore affecting penetration (the degree of which was associated with the formation of a more distinct vortex ring structure).…”

Section: Introductionmentioning

confidence: 99%

The Flow Structure Produced by Pulsed-jet Vortex Generators in a Turbulent Boundary Layer in an Adverse Pressure Gradient

Kostas¹,

Foucaut²,

Stanislas³

2007

Flow Turbulence Combust

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The effect of pulsed jet vortex generators on the structure of an adverse pressure gradient turbulent boundary layer flow was investigated. Two geometrically optimised vortex generator configurations were used, co-rotating and counterrotating. The duty cycle and pulse frequency were both varied and measurements of the skin friction (using hot films) and flow structure (using stereo PIV) were performed downstream of the actuators. The augmentation of the mean wall shear stress was found to be dependent on the net mass flow injected by the actuators. A quasi steady flow structure was found to develop far downstream of the injection location for the highest pulse frequency tested. The actuator near field flow structure was observed to respond very quickly to variations in the jet exit velocity.

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“…This transition has important implications for jet structure (Getsinger et al 2014) as well as the type of transverse jet control required to impact jet behaviour (M'Closkey et al 2002;Shapiro et al 2006;Davitian et al 2010b). The evidence for transition in the upstream shear layer instability has been documented for both the equidensity and low-density JICF via alterations in the shear layer's spectral character, reduction in the energy transfer from fundamental to subharmonic frequencies along the shear layer, altered responses to low-level forcing, evidence of a Hopf bifurcation and other relevant observations (Megerian et al 2007;Davitian et al 2010a;Getsinger et al 2012).…”

mentioning

confidence: 98%

Transverse jet mixing characteristics

et al. 2016

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This experimental study explores and quantifies mixing characteristics associated with a gaseous round jet injected perpendicularly into cross-flow for a range of flow and injection conditions. The study utilizes acetone planar laser-induced fluorescence imaging to determine mixing metrics in both centreplane and cross-sectional planes of the jet, for a range of jet-to-cross-flow momentum flux ratios (2 J 41), density ratios (0.35 S 1.0) and injector configurations (flush nozzle, flush pipe and elevated nozzle), all at a fixed jet Reynolds number of 1900. For the majority of conditions explored, there is a direct correspondence between the nature of the jet's upstream shear layer instabilities and structure, as documented in detail in Getsinger et al. (J. Fluid Mech., vol. 760, 2014, pp. 342-367), and the jet's mixing characteristics, consistent with diffusion-dominated processes, but with a few notable exceptions. When quantified as a function of distance along the jet trajectory, mixing metrics for jets in cross-flow with an absolutely unstable upstream shear layer and relatively symmetric counter-rotating vortex pair cross-sectional structure tend to show better local molecular mixing than for jets with convectively unstable upstream shear layers and generally asymmetric cross-sectional structures. Yet the spatial evolution of mixing with downstream distance can be greater for a few specific convectively unstable conditions, apparently associated with the initiation and nature of shear layer rollup as a trigger for improved mixing. A notable exception to these trends concerns conditions where the equidensity jet in cross-flow has an upstream shear layer that is already absolutely unstable, and the jet density is then reduced in comparison with that of the cross-flow. Here, density ratios below unity tend to mix less well than for equidensity conditions, demonstrated to result from differences in the nature of higher-density cross-flow entrainment into lower-density shear layer vortices.

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Optimization of Controlled Jets in Crossflow

Cited by 81 publications

References 19 publications

A turbulent jet in crossflow analysed with proper orthogonal decomposition

A turbulent jet in crossflow analysed with proper orthogonal decomposition

The Flow Structure Produced by Pulsed-jet Vortex Generators in a Turbulent Boundary Layer in an Adverse Pressure Gradient

Transverse jet mixing characteristics

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