Measurements of scalar power spectra in high Schmidt number turbulent jets

Miller, Paul L.; Dimotakis, Paul E.

doi:10.1017/s0022112096001425

Cited by 77 publications

(55 citation statements)

References 23 publications

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“…These differences are more pronounced at larger Sc and can be considered in terms of Batchelor's theory for scalar behavior 19 and experimentallyobserved high-Schmidt number scalar behavior. [20][21][22][23] …”

Section: Implications For High-schmidt Number Scalar Mixingmentioning

confidence: 99%

“…In contradiction to Batchelor's 19 prediction, several experimental studies of high Schmidt number turbulent scalars have not observed the κ −1 scaling behavior. [20][21][22][23] Some observed that a weaker scaling, possibly a lognormal scaling, across the viscous-convective subrange may be more representative of experimental data. 20 Case 5 has a sufficiently high Sc = 256 to allow for a comparison of the scalar spectra produced by the linear scalar and mean gradient forcing methods to both Batchelor's 19 predictions and the summarized experimental results.…”

Section: -15mentioning

confidence: 99%

“…[20][21][22][23] Some observed that a weaker scaling, possibly a lognormal scaling, across the viscous-convective subrange may be more representative of experimental data. 20 Case 5 has a sufficiently high Sc = 256 to allow for a comparison of the scalar spectra produced by the linear scalar and mean gradient forcing methods to both Batchelor's 19 predictions and the summarized experimental results. As the Reynolds number is low (Re λ ≈ 8), it is not expected to capture the κ −5/3 scaling across the inertial-convective range as predicted by Obukhov 25 and Corrsin, 24 but it is expected that the Schmidt number is high enough to capture the correct behavior across the viscous-convective range.…”

Section: -15mentioning

confidence: 99%

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A novel forcing technique to simulate turbulent mixing in a decaying scalar field

2013

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To realize the full potential of Direct Numerical Simulation in turbulent mixing studies, it is necessary to develop numerical schemes capable of sustaining the flow physics of turbulent scalar quantities. In this work, a new scalar field forcing technique, termed "linear scalar forcing," is presented and evaluated for passive scalars. It is compared to both the well-known mean scalar gradient forcing technique and a low waveshell spectral forcing technique. The proposed forcing is designed to capture the physics of one-time scalar variance injection and the subsequent self-similar turbulent scalar field decay, whereas the mean scalar gradient forcing and low waveshell forcing techniques are representative of continuous scalar variance injection. The linear scalar forcing technique is examined over a range of Schmidt numbers, and the behavior of the proposed scalar forcing is analyzed using single and two-point statistics. The proposed scalar forcing technique is found to be perfectly isotropic, preserving accepted scalar field statistics (fluxes) and distributions (scalar quantity, dissipation rate). Additionally, it is found that the spectra resulting from the three scalar forcing techniques are comparable for unity Schmidt number conditions, but differences manifest at high Schmidt numbers. These disparities are reminiscent of those reported between scaling arguments suggested by theoretical predictions and experimental results for the viscous-convective subrange. C 2013 AIP Publishing LLC. [http://dx

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Section: Implications For High-schmidt Number Scalar Mixingmentioning

confidence: 99%

Section: -15mentioning

confidence: 99%

Section: -15mentioning

confidence: 99%

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A novel forcing technique to simulate turbulent mixing in a decaying scalar field

2013

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“…Note that only a few experiments (14), (15) have exhibited a distinct -1 power decay region. Further discussion is required on the form of the viscous-convective power spectrum (16), (17) , which is beyond the scope of this paper. Figure 5 shows the cospectra and coherences between v and c. The cospectrum is normalized by the mean velocity U and the initial concentration C. The cospectrum is defined as…”

Section: Power Spectra and Cross Spectra In The Neutral Stratificationmentioning

confidence: 99%

Velocity and Passive Scalar Cross Spectra in Stably and Unstably Stratified Grid Turbulence

Nagata

Sakai

Komori

et al. 2007

JFST

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The effects of stable and unstable thermal stratifications on the cross spectra between passive scalar (dye concentration) fluctuation c and vertical velocity fluctuation v in shear-free grid turbulence are investigated using previously published data. The results show that cospectra in the neutral stratification have a slope close to -7/3, as predicted by Lumley (1964). The coherences of v and c in the neutral stratification have a slope close to -4/3, which implies the absence of a phase shift between v and c. In the weakly stable stratification, both the cospectrum and the coherence decay due to stable buoyancy force. In the moderately stable stratification, the scaling laws of the cospectrum and coherence collapse in the downstream region. However, in the strongly stable stratification, the negative cospectrum in the countergradient region reconstructs a small but distinct region close to -7/3 after the collapse. In the unstable stratification, despite strong convective motions due to the unstable buoyancy force, the cospectra and the coherences exhibit -7/3 and -4/3 power decay regions, respectively.

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“…The jet in crossflow (Pratte & Baines 1967;Andreopoulos & Rodi 1984;Andreopoulos 1985;Smith & Mungal 1998;Shan & Dimotakis 2006) is characterized by higher entrainment rate than a jet into a quiescent reservoir (e.g. Becker, Hottel & Williams 1967;Dowling & Dimotakis 1990;Miller & Dimotakis 1996). In supersonic crossflow (Zukoski & Spaid 1964;Spaid & Zukoski 1968;Hollo, McDaniel & Hartfield 1994;Ben-Yakar, Mungal & Hanson 2006), a bow shock forms, causing the boundary layer to separate, creating a flameholding region where fuel and air can mix subsonically.…”

Section: Introductionmentioning

confidence: 99%

Large-eddy simulation of mixing in a recirculating shear flow

et al. 2010

Self Cite

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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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Measurements of scalar power spectra in high Schmidt number turbulent jets

Cited by 77 publications

References 23 publications

A novel forcing technique to simulate turbulent mixing in a decaying scalar field

A novel forcing technique to simulate turbulent mixing in a decaying scalar field

Velocity and Passive Scalar Cross Spectra in Stably and Unstably Stratified Grid Turbulence

Large-eddy simulation of mixing in a recirculating shear flow

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