On conditional scalar increment and joint velocity–scalar increment statistics

Zhang, Hengbin; Wang, Danhong; Tong, Chenning

doi:10.1088/1367-2630/6/1/038

Cited by 3 publications

(2 citation statements)

References 35 publications

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“…Uberoi & Freymuth 1969;Wygnanski & Fielder 1969;Birch et al 1978;Dowling & Dimotakis 1990;Antonia & Mi 1993). Furthermore, in those cases where some data is available, it is often limited to a few quantities (Kounalakis, Sivathanu & Faeth 1991;Renfro et al 2000) usually not including the velocity field, except for Zhang, Wang & Tong (2004) who reported velocity-scalar increment p.d.f.. The experimental measurements by Wang et al (2005) and Nagel & Dahm (2007) have been used to investigate the effects of variable density on the turbulence spectra.…”

Section: Introductionmentioning

confidence: 99%

On the effect of heat release in turbulence spectra of non-premixed reacting shear layers

Knaus

Pantano

2009

J. Fluid Mech.

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Velocity, mixture fraction and temperature spectra obtained from five direct numerical simulations of non-reacting and reacting shear layers, using the infinitely fast chemistry approximation, are analysed. Two different global chemical reactions corresponding to methane and hydrogen combustion with air, respectively, are considered. The effect of heat release, i.e. density variation, on the inertial and dissipation turbulence subrange of the spectra is investigated. Analysis of the database supports the experimentally available measurements of spectra in turbulent reacting flows showing that heat release effects can be scaled out by utilizing Favre-averaged (density-weighted) largescale turbulence quantities. This is supported by the simulation results for velocity and mixture fraction in our moderate-Reynolds-number flows but it appears to be less supported in the dissipation subrange of the temperature spectra. The departure from universal scaling using Favre-averaged quantities in the temperature spectrum, which is evident in the dissipation subrange, appears to be caused by the strong nonlinearity of the state relationship relating the mixture fraction to the temperature, as has been suggested previously. These effects are less pronounced at intermediate wavenumbers.Analysis suggests that the nonlinear state relationship and the spectra of mixture fraction moments can be used to reconstruct the temperature spectrum across the flow. Moreover, the governing equation for the temperature variance is analysed to identify a possible surrogate for the overall rate of dissipation of temperature fluctuations and their corresponding dissipation length scale. This scaling analysis is then used to separate planes across the shear layer where the temperature dissipation length scale is alike that of the mixture fraction from regions where smaller length scales are present, and are evidenced in the dissipation subrange using Kolmogorov scaling. In our simulations, these regions correspond to the centre of the shear layer and the mean flame location. The new estimate for the temperature dissipation length scale is able to collapse the compensated spectra profiles at all planes across the shear layer for all simulations.

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Section: Introductionmentioning

confidence: 99%

On the effect of heat release in turbulence spectra of non-premixed reacting shear layers

Knaus

Pantano

2009

J. Fluid Mech.

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“…The statistics of such a conditional scalar is well described by the Kolmogorov-Obukhov-Corrsin theory. The locally averaged scalar dissipation rate and the scalar variance spectral transfer rate are lower than the mean scalar dissipation rate [27]. In the spirit of the Kolmogorov's refined similarity hypotheses, the local conditional Péclet number is expected to be lower than that based on the unconditioned statistics.…”

Section: Brief Description Of the Methodsmentioning

confidence: 92%

Noise Correction and Length Scale Estimation for Scalar Dissipation Rate Measurements in Turbulent Partially Premixed Flames

Cai

Karpetis

Tong

2010

Flow Turbulence Combust

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A recently developed conditional sampling-based method for correcting noise effects in scalar dissipation rate measurements and for estimating the extent of resolution of the dissipation rate is employed to analyze the data obtained in turbulent partially premixed (Sandia) flames. The method uses conditional sampling to select instantaneous fully resolved local scalar fields, which are analyzed to determine the measurement noise and to correct the Favre mean, conditional, and conditionally filtered dissipation rates. The potentially under-resolved local scalar fields, also selected using conditional sampling, are corrected for noise and are analyzed to examine the extent of resolution. The error function is used as a model for the potentially under-resolved local scalar to evaluate the scalar dissipation length scales and the percentage of the dissipation resolved. The results show that the Favre mean dissipation rate, the mean dissipation rate conditional on the mixture fraction, and dissipation rate filtered conditionally on the mixture fraction generally are well resolved in the flames. Analyses of the dissipation rates filtered conditionally on the mixture fraction and temperature show that the length scale increases with temperature, due to lower dissipation rate and higher diffusivity. The dissipation rate is well resolved for temperatures above 1,300 K but is less resolved at lower temperatures, although the probability of very low temperature events is Submitted for the special issue dedicated to S.B. Pope.Flow Turbulence Combust (2010) 85:309-332 low. To fully resolve these rare events the sample spacing needs to be reduced by approximately one half. The present study further demonstrates the effectiveness of the new noise correction and length scale estimation method.

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Large eddy simulation of a lifted ethylene flame using a dynamic nonequilibrium model for subfilter scalar variance and dissipation rate

Kaul

Raman

Knudsen

et al. 2013

Proceedings of the Combustion Institute

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Accurate prediction of nonpremixed turbulent combustion using large eddy simulation (LES) requires detailed modeling of the mixing between fuel and oxidizer at scales finer than the LES filter resolution. In conserved scalar combustion models, the small scale mixing process is quantified by two parameters, the subfilter scalar variance and the subfilter scalar dissipation rate. The most commonly used models for these quantities assume a local equilibrium exists between production and dissipation of variance. Such an assumption has limited validity in realistic, technically relevant flow configurations. However, nonequilibrium models for variance and dissipation rate typically contain a model coe cient whose optimal value is unknown a priori for a given simulation. Furthermore, conventional dynamic procedures are not useful for estimating the value of this coe cient. In this work, an alternative dynamic procedure based on the transport equation for subfilter scalar variance is presented, along with a robust conditional averaging approach for evaluation of the

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On conditional scalar increment and joint velocity–scalar increment statistics

Cited by 3 publications

References 35 publications

On the effect of heat release in turbulence spectra of non-premixed reacting shear layers

On the effect of heat release in turbulence spectra of non-premixed reacting shear layers

Noise Correction and Length Scale Estimation for Scalar Dissipation Rate Measurements in Turbulent Partially Premixed Flames

Large eddy simulation of a lifted ethylene flame using a dynamic nonequilibrium model for subfilter scalar variance and dissipation rate

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