Multi-particle model of coarse-grained scalar dissipation rate with volumetric tensor in turbulence

Tanaka, Shusei; Watanabe, Tomoaki; Nagata, Koji

doi:10.1016/j.jcp.2019.03.034

Cited by 8 publications

(14 citation statements)

References 63 publications

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“…Numerical schemes except for the filter are the same as those used in the DNS. This LES code was also used for implicit LES of turbulent planar jets and turbulent boundary layers with a passive scalar transfer, where the code was validated by comparison with DNS and experiments (Tanaka, Watanabe & Nagata 2019; Watanabe et al. 2019 b ).…”

Section: Implicit Les and Dns Of A Stably Stratified Shear Layermentioning

confidence: 99%

Large-scale characteristics of a stably stratified turbulent shear layer

Watanabe

Nagata

2021

J. Fluid Mech.

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Implicit large eddy simulation is performed to investigate large-scale characteristics of a temporally evolving, stably stratified turbulent shear layer arising from the Kelvin–Helmholtz instability. The shear layer at late time has two energy-containing length scales: the scale of the shear layer thickness, which characterizes large-scale motions (LSM) of the shear layer; and the larger streamwise scale of elongated large-scale structures (ELSS), which increases with time. The ELSS forms in the middle of the shear layer when the Richardson number is sufficiently large. The contribution of the ELSS to velocity and density variances becomes relatively important with time although the LSM dominate the momentum and density transport. The ELSS have a highly anisotropic Reynolds stress, to a degree similar to the near-wall region of turbulent boundary layers, while the Reynolds stress of the LSM is as anisotropic as in the outer region. Peaks in the spectral energy density associated with the ELSS emerge because of the slow decay of turbulence at very large scales. A forward interscale energy transfer from large to small scales occurs even at a small buoyancy Reynolds number. However, an inverse transfer also occurs for the energy of spanwise velocity. Negative production of streamwise velocity and density spectra, i.e. counter-gradient transport of momentum and density, is found at small scales. These behaviours are consistent with channel flows, indicating similar flow dynamics in the stratified shear layer and wall-bounded shear flows. The structure function exhibits a logarithmic law at large scales, implying a $k^{-1}$ scaling of energy spectra.

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Section: Implicit Les and Dns Of A Stably Stratified Shear Layermentioning

confidence: 99%

Large-scale characteristics of a stably stratified turbulent shear layer

Watanabe

Nagata

2021

J. Fluid Mech.

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“…. 20 This model is developed on the basis of the estimation for coarse-grained gradients with a volumetric tensor 33 and an SGS model for filtered scalar dissipation rate, which was originally developed for LES of scalar mixing. 19 The model relies on the shape of an energy spectrum of scalar fluctuations and is referred to as a scalar spectrum model.…”

Section: A Scalar Spectrum Model For Coarse-grained Scalar Dissipatio...mentioning

confidence: 99%

“…18,19 One of the SGS models was reformulated for the MVM to model the coarse-grained scalar dissipation rate in LPS. 20 Previous studies have shown that LES/LPS with the MVM can accurately model molecular diffusion in incompressible turbulence. 5,21 There are several variants of the MVM with differences in the number of particles to model the molecular diffusion or in the detailed relaxation process to the average.…”

Section: Introductionmentioning

confidence: 99%

“…The MVM was shown to work better with about 12 particles than fewer particles. 17,20 In addition, comparisons between LES/LPS and experiments of a reactive scalar mixing layer have shown that the mixing and reaction are better predicted with the IEM-type relaxation scheme than with that of Curl's model. 5 These studies have reported both a priori and posteriori tests of the MVM in incompressible flows, proving the effectiveness of LES/LPS with the MVM in predicting mixing and reactions in turbulent flows.…”

Section: Introductionmentioning

confidence: 99%

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Hybrid large eddy simulation and Lagrangian simulation of a compressible turbulent planar jet with a chemical reaction

Xing,

Watanabe,

Nagata

2024

Numerical Methods in Fluids

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Large eddy simulation (LES) coupled with Lagrangian particle simulation (LPS) is applied to investigate high‐speed turbulent reacting flows. Here, LES solves a velocity field while LPS solves scalar transport equations with notional particles. Although LPS does not require sub‐grid scale models for chemical source terms, molecular diffusion has to be modeled by a so‐called mixing model, for which a mixing volume model (MVM), that is originally proposed for an inert scalar in incompressible flow, is extended to reactive scalars in compressible flows. The extended model is based on a relaxation process toward the average of nearby notional particles and assumes a common mixing timescale for all species. LES/LPS with the MVM is applied to a temporally‐evolving compressible turbulent planar jet with an isothermal reaction and is tested by comparing the results with direct numerical simulation (DNS). The results show that LES/LPS well predicts the statistics of mass fractions. As the jet Mach number increases, the reaction progress delays due to the delayed jet development. This Mach number dependence is also well reproduced in LES/LPS. The mean molecular diffusion term of the product calculated as a function of its mass fraction also agrees well between LES/LPS and DNS. An important parameter for the MVM is the distance among particles, for which the requirement for accurate prediction is presented for the present test case. LES/LPS with the MVM is expected to be a promising method for investigating compressible turbulent reactive flows at a moderate computational cost.

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“…1998) are applied for spatial discretization, where the accuracy is fourth order in the and directions, and second order in the direction. The third-order Runge–Kutta method is used for temporal advancement, while the biconjugate gradient stabilized (Bi-CGSTAB) method (Van der Vorst 1992) is used to solve the Poisson equation for pressure. An early time period of the flow is simulated by using an implicit large eddy simulation (ILES) like the one conducted in our previous study (Tanaka, Watanabe & Nagata 2019), where the effects of subgrid scales are modelled implicitly by a tenth-order low-pass filter presented in Kennedy & Carpenter (1994), while other numerical schemes are the same as in the DNS. After the TBL fully develops in the ILES, the ILES results are used to initialize the DNS.…”

Section: Tablementioning

confidence: 99%

Reynolds number dependence of the turbulent/non-turbulent interface in temporally developing turbulent boundary layers

2023

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Direct numerical simulations (DNS) of temporally developing turbulent boundary layers are performed with a wide range of Reynolds numbers based on the momentum thickness $Re_{\theta } = 2000$ – $13\,000$ for investigating the Reynolds number dependence of the turbulent/non-turbulent interface (TNTI) layer. The grid spacing in the DNS is determined carefully such that small-scale turbulent motions near the TNTI are well resolved. The outer edge of the TNTI layer, called the irrotational boundary, is detected with vorticity magnitude. The mean thicknesses of the TNTI layer, $\delta _{TNTI}$ , turbulent sublayer, $\delta _{TSL}$ , and viscous superlayer, $\delta _{VSL}$ , are found to be approximately $15\eta _{TI}$ , $10\eta _{TI}$ and $5\eta _{TI}$ , respectively, where $\eta _{TI}$ is the Kolmogorov scale taken in the turbulent region near the TNTI layer. The mean curvature of the irrotational boundary is also characterized by $\eta _{TI}$ . The shear parameter and the shear-to-vorticity ratio show that the mean shear effects near the TNTI layer are not significant for both large and small scales. The anisotropy tensors of Reynolds stress and vorticity suggest that the turbulence under the TNTI layer tends to be isotropic at high $Re_{\theta }$ , for which $\eta _{TI}/\delta \sim Re_{\theta }^{-3/4}$ is valid with the boundary layer thickness $\delta$ . The surface area of the irrotational boundary is consistent with the fractal analysis of the interface, where the fractal dimension $D_f$ is found to be $2.14$ – $2.20$ . The present results suggest that the mean entrainment rate per unit horizontal area normalized by the friction velocity varies slowly as $Re_{\theta }^{(3/4)(D_f-2)}$ for $Re_{\theta } \geq 4000$ .

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Multi-particle model of coarse-grained scalar dissipation rate with volumetric tensor in turbulence

Cited by 8 publications

References 63 publications

Large-scale characteristics of a stably stratified turbulent shear layer

Large-scale characteristics of a stably stratified turbulent shear layer

Hybrid large eddy simulation and Lagrangian simulation of a compressible turbulent planar jet with a chemical reaction

Reynolds number dependence of the turbulent/non-turbulent interface in temporally developing turbulent boundary layers

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