Molecular Mixing and Flowfield Measurements in a Recirculating Shear Flow. Part II: Supersonic Flow

Bonanos, Aristides M.; Bergthorson, Jeffrey M.; Dimotakis, Paul E.

doi:10.1007/s10494-009-9199-x

Cited by 6 publications

(5 citation statements)

References 29 publications

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“…The experiments reported here are mixing-limited, as no decrease in the total amount of chemical product was observed with a reduction in chemical-kinetic rates. Similar experiments for supersonic free-stream flow were also shown to be in the mixinglimited regime for Da > 1.5 [26,42]. Temperature profiles in these experiments are fit using an asymmetric function,…”

Section: Appendix: Flip Experimentsmentioning

confidence: 73%

“…Note that the recirculating flow enhances chemical reactivity further, by providing the opportunity for the re-entrainment of hot products, so that a free-shear layer at a lower Da might not react to completion when the present one will. The experiments reported here were all performed with kinetics that result in Da above this limiting value, and mixing-limited combustion was also verified experimentally (see Appendix and [26,42]). …”

Section: Mixing With Expansion-ramp Injectionmentioning

confidence: 74%

“…The supersonic flow results are presented in an accompanying article [26]. The variation of the flowfield with variable levels of mass injection and heat release are studied.…”

Section: Introductionmentioning

confidence: 99%

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Molecular Mixing and Flowfield Measurements in a Recirculating Shear Flow. Part I: Subsonic Flow

Bergthorson

Johnson

Bonanos

et al. 2009

Flow Turbulence Combust

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The mixing and flowfield of a complex geometry, similar to a rearwardfacing step flow but with injection, is studied. A subsonic top-stream is expanded over a perforated ramp at an angle of 30 • , through which a secondary stream is injected. The mass flux of the second stream is chosen to be insufficient to provide the entrainment requirements of the shear layer, which, as a consequence, attaches to the lower guidewall. Part of the flow is directed upstream forming a re-entrant jet within the recirculation zone that enhances mixing and flameholding. A control-volume model of the flow is found to be in good agreement with the variation of the overall pressure coefficient of the device with variable mass injection. The flowfield response to changing levels of heat release is also quantified. While increased heat release acts somewhat analogously to increased mass injection, fundamental differences in the flow behaviour are observed. The hypergolic hydrogen-fluorine chemical reaction employed allows the level of molecular mixing in the flow to be inferred. The amount of mixing is found to be higher in the expansion-ramp geometry than in classical freeshear layers. As in free-shear layers, the level of mixing is found to decrease with increasing top-stream velocity. Results for a similar configuration with supersonic flow in the top stream are reported in Part II of this two-part series.

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Section: Appendix: Flip Experimentsmentioning

confidence: 73%

Section: Mixing With Expansion-ramp Injectionmentioning

confidence: 74%

See 1 more Smart Citation

Molecular Mixing and Flowfield Measurements in a Recirculating Shear Flow. Part I: Subsonic Flow

Bergthorson

Johnson

Bonanos

et al. 2009

Flow Turbulence Combust

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“…The experiments are performed at the GALCIT supersonic shear-layer laboratory ( S 3 L ), a blowdown facility with test times on the order of seconds (e.g., Hall 1991;Slessor 1998;Bond 1999;Bergthorson et al 2009;Bonanos et al 2009).…”

Section: Facility Overviewmentioning

confidence: 99%

Simulating schlieren and shadowgraph images from LES data

et al. 2019

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Geometrical optics ray-tracing is used to derive schlieren and shadowgraph images from large-eddy simulation (LES) data of a jet in supersonic crossflow and to compare with experimental data. Including the components of the optical system that forms the image in the simulation is found to be important. The technique produces images that replicate flow physics more faithfully than straight-line path integration and other techniques, and more efficiently than physical-optics techniques. Applications of these simulated images are demonstrated in supersonic flows. Time-correlated pairs of shadowgraph images taken from the LES using this technique are used in conjunction with an image-correlation velocimetry technique to compare the estimated convection velocity field in the LES to that of experiments of the same flow. Agreement between the two is good with a maximum variance of 5% by some metrics. This technique can aid in the validation of LES results, allowing quantitative comparison between experiment and simulation, and to extract information unattainable by experiment alone. Comparisons of simulated and experimental jet penetration into the supersonic freestream are also made.

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“…This second mixing layer allows products to further mix with the bottom-stream fluid. The recirculating region, reentrant jet and the secondary shear layer lead to enhanced mixing compared to a free-shear layer, while providing a low strain-rate environment that is important for flameholding (Johnson 2005;Bergthorson et al 2009;Bonanos et al 2009). …”

Section: The Expansion-ramp Injection Geometrymentioning

confidence: 99%

Large-eddy simulation of mixing in a recirculating shear flow

et al. 2010

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The flow field and mixing in an expansion-ramp geometry is studied using large-eddy simulation (LES) with subgrid scale (SGS) modelling. The expansion-ramp geometry was developed to investigate enhanced mixing and flameholding characteristics while maintaining low total-pressure losses. Passive mixing was considered without taking into account the effects of chemical reactions and heat release, an approximation that is adequate for experiments conducted in parallel. The primary objective of the current work is to validate the LES-SGS closure in the case of passive turbulent mixing in a complex configuration and, if successful, to rely on numerical simulation results for flow details unavailable via experiment. Total (resolved-scale plus subgrid contribution) probability density functions (p.d.f.s) of the mixture fraction are estimated using a presumed beta-distribution model for the subgrid field. Flow and mixing statistics are in good agreement with the experimental measurements, indicating that the mixing on a molecular scale is correctly predicted by the LES-SGS model. Finally, statistics are shown to be resolution-independent by computing the flow for three resolutions, at twice and four times the resolution of the coarsest simulation.

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Molecular Mixing and Flowfield Measurements in a Recirculating Shear Flow. Part II: Supersonic Flow

Cited by 6 publications

References 29 publications

Molecular Mixing and Flowfield Measurements in a Recirculating Shear Flow. Part I: Subsonic Flow

Molecular Mixing and Flowfield Measurements in a Recirculating Shear Flow. Part I: Subsonic Flow

Simulating schlieren and shadowgraph images from LES data

Large-eddy simulation of mixing in a recirculating shear flow

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