Stochastic geometric properties of scalar interfaces in turbulent jets

Miller, Paul L.; Dimotakis, Paul E.

doi:10.1063/1.857876

Cited by 60 publications

(69 citation statements)

References 18 publications

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“…2a). It is a smoothly-increasing function of scale, bounded by its limiting value of unity (topological dimension), at the smallest scales, and 2 (embedding dimension), at the largest scales (cf., also, Miller & Dimotakis 1991). A similar behavior obtains for lower and higher values of the scalar threshold.…”

Section: Isoscalar Geometry In Turbulent Jetssupporting

confidence: 56%

See 1 more Smart Citation

On the geometry of two-dimensional slices of irregular level sets in turbulent flows

Dimotakis¹,

Catrakis²,

Cook³

et al. 1999

Fundamental Problematic Issues in Turbulence

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Isoscalar surfaces in turbulent flows are found to be more complex than (selfsimilar) fractals, in both the far field of liquid-phase turbulent jets and in a realization of Rayleigh-Taylor-instability flow. In particular, they exhibit a scaledependent coverage dimension, D 2 (λ), for 2-D slices of scalar level sets, that increases with scale, from unity, at small scales, to 2, at large scales. For the jet flow and Reynolds numbers investigated, the isoscalar-surface geometry is both scalarthreshold-and Re-dependent; the level-set (coverage) length decreases with increasing Re, indicating enhanced mixing with increasing Reynolds number; and the size distribution of closed regions is well described by lognormal statistics at small scales. A similar D 2 (λ) behavior is found for level-set data of 3-D density-interface behavior in recent direct numerical-simulation studies of Rayleigh-Taylor-instability flow. A comparison of (spatial) spectral and isoscalar coverage statistics will be discussed.

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Section: Isoscalar Geometry In Turbulent Jetssupporting

confidence: 56%

“…for a coverage count normalized at λ = δ, i.e., for N d (δ) = 1 (Takayasu 1982(Takayasu , 1992Miller & Dimotakis 1991;Dimotakis 1991;and Catrakis & Dimotakis 1996a). A more complete discussion of these notions can be found in the review by .…”

Section: Fractals and Scale-dependent Irregular Level Setsmentioning

confidence: 99%

On the geometry of two-dimensional slices of irregular level sets in turbulent flows

Dimotakis¹,

Catrakis²,

Cook³

et al. 1999

Fundamental Problematic Issues in Turbulence

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show abstract

“…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%

“…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%

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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“…Certain experiments and simulations support the scaling, [2][3][4][5] whereas others contradict it. [6][7][8] There even exist certain theoretical objections to the κ −1 scaling, based on the requirement of boundedness of the scalar variance.…”

Section: Introductionmentioning

confidence: 99%

On filtering in the viscous-convective subrange for turbulent mixing of high Schmidt number passive scalars

Verma

Blanquart

2013

Physics of Fluids

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In the present work, we investigate the possibility of performing velocity-resolved, scalar-filtered (VR-SF) numerical simulations of turbulent mixing of high Schmidt number scalars, by using a Large Eddy Simulation (LES)-type filter in the viscousconvective subrange. The only requirement for this technique is the large scale separation between the Kolmogorov and Batchelor length scales, which is a direct outcome of the high Schmidt number of the scalar. The present a priori analysis using high fidelity direct numerical simulation data leads to two main observations. First, the missing triadic interactions between (resolved) velocity and (filtered-out) scalar modes in the viscous-convective subrange do not affect directly the large scales. Second, the magnitude of the subgrid term is shown to be extremely small, which makes it particularly susceptible to numerical errors associated with the scalar transport scheme. A posteriori tests indicate that upwinded schemes, generally used for LES in complicated geometries, are sufficiently dissipative to overwhelm any contribution from the subgrid term. This renders the subgrid term superfluous, and as a result, VR-SF simulations run without subgrid scalar flux models are able to preserve large scale transport characteristics with remarkable accuracy. C 2013 AIP Publishing LLC. [http://dx

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Stochastic geometric properties of scalar interfaces in turbulent jets

Cited by 60 publications

References 18 publications

On the geometry of two-dimensional slices of irregular level sets in turbulent flows

On the geometry of two-dimensional slices of irregular level sets in turbulent flows

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

On filtering in the viscous-convective subrange for turbulent mixing of high Schmidt number passive scalars

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