Balance of turbulence energy in the region of jet-flow establishment

Sami, Sedat

doi:10.1017/s0022112067000643

Cited by 22 publications

(11 citation statements)

References 3 publications

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“…In Fig. 12 showing the total dissipation, the LES results are roughly coincident with the existing values [5,6]. Accuracy in predicting dissipation should be a background for validity of mean flow and its fluctuation.…”

Section: Flow Fieldsupporting

confidence: 74%

Large eddy simulation of flow and scalar transport in a round jet

Suto¹,

Matsubara²,

Kobayashi³

et al. 2004

Heat Trans. Asian Res.

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Large eddy simulation (LES) was performed for a spatially developing round jet and its scalar transport at four steps of Reynolds number set between 1200 and 1,000,000. A simulated domain, which extends 30 times the nozzle diameter, includes initial, transitional, and established stage of jet. A modified version of convection outflow condition was proposed in order to diminish the effect of a downstream boundary. Tested were two kinds of subgrid scale (SOS) models: a Smagorinsky model (SM) and a dynamic Smagorinsky model (DSM). In the former model, parameters are kept at empirically deduced constants, while in the latter, they are calculated using different levels of space filtering. Data analysis based on the decay law of jet clearly presented the performance of SGS models. Simulated results by SM and DSM compared favorably with existing measurements of jet and its scalar transport. However, the quantitative accuracy of DSM was better than that of SM at a transitional stage of flow field. Computed parameters by DSM, coefficient for SGS stresses, C R , and SGS eddy diffusivity ratio, Γ SGS , were not far from empirical constants of SM.Optimization of the model coefficient was suggested in DSM so that coefficient C R was nearly equal in the established stage of jet but it was reduced in low turbulence close to the jet nozzle.

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Section: Flow Fieldsupporting

confidence: 74%

Large eddy simulation of flow and scalar transport in a round jet

Suto¹,

Matsubara²,

Kobayashi³

et al. 2004

Heat Trans. Asian Res.

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show abstract

“…Two flow regions have been distinguished: the flowestablishment region and, farther in the downstream direction, the self-preservation or self-similarity region where the flow profiles across the jet are self-similar. During the sixties, some researchers including Davies, Fisher & Barratt (1962), Sami, Carmody & Rouse (1967) and Sami (1967) studied turbulence in the first jet region. Wygnanski & Fiedler (1969) also made some measurements of flow quantities in the self-similarity region of a jet at Reynolds number Re D = u j D/ν = 10 5 , where u j is the jet nozzle exit velocity, D the diameter and ν the molecular viscosity.…”

Section: Introductionmentioning

confidence: 99%

Turbulence and energy budget in a self-preserving round jet: direct evaluation using large eddy simulation

2009

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An axisymmetric jet at a diameter-based Reynolds number of 1.1 × 10 4 is computed by a large eddy simulation (LES) in order to investigate its self-similarity region. The LES combines low-dissipation numerical schemes and explicit filtering of the flow variables to relax energy through the smaller scales discretized. The computational domain extends up to 150 jet radii in the downstream direction, which is found to be large enough to discretize a part of this region. Turbulence in the self-preserving jet is characterized by evaluating explicitly from the LES fields the second-and third-order moments of velocity, the pressure-velocity correlations as well as the budgets for the turbulent kinetic energy and for its components. Reference solutions are thus obtained. They agree well with the experimental data given by Panchapakesan & Lumley (J. at a higher Reynolds number, specially regarding the turbulence diffusion and the dissipation, are discussed. They appear largely resulting from the approximations made in the experiments to estimate the quantities that cannot be measured with accuracy. The role of the pressure terms in the energy redistribution is also clarified by the LES. Moreover, the turbulent energy budget is calculated in the jet from an equation derived from the filtered compressible Navier-Stokes equations, which includes the dissipation due to the explicit filtering. This has allowed us to assess the behaviour of the LES approach based on relaxation filtering (LES-RF) from the contributions of filtering and viscosity to energy dissipation. The filtering activity is particularly shown to adjust by itself to the grid and flow properties.

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“…The approximate solution for normalized turbulent energy dissipate rate ( / 3 ), compared with the experimental data of Wygnanski and Fielder as well as with that of Sami [19], is shown in Figure 12. The available experimental data on (ii) Swirl Jet.…”

Section: 4mentioning

confidence: 98%

Development of a Nonlinear k-ε Model Incorporating Strain and Rotation Parameters for Prediction of Complex Turbulent Flows

Ali

Hosoda

Kimura

2015

International Journal of Partial Differential Equations

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The standard -model has the deficiency of predicting swirling and vortical flows due to its isotropic assumption of eddy viscosity. In this study, a second-order nonlinear -model is developed incorporating some new functions for the model coefficients to explore the models applicability to complex turbulent flows. Considering the realizability principle, the coefficient of eddy viscosity ( ) is derived as a function of strain and rotation parameters. The coefficients of nonlinear quadratic term are estimated considering the anisotropy of turbulence in a simple shear layer. Analytical solutions for the fundamental properties of swirl jet are derived based on the nonlinear -model, and the values of model constants are determined by tuning their values for the best-fitted comparison with the experiments. The model performance is examined for two test cases: (i) for an ideal vortex (Stuart vortex), the basic equations are solved numerically to predict the turbulent structures at the vortex center and the (ii) unsteady 3D simulation is carried out to calculate the flow field of a compound channel. It is observed that the proposed nonlinear -model can successfully predict the turbulent structures at vortex center, while the standard -model fails. The model is found to be capable of accounting the effect of transverse momentum transfer in the compound channel through generating the horizontal vortices at the interface.

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Balance of turbulence energy in the region of jet-flow establishment

Cited by 22 publications

References 3 publications

Large eddy simulation of flow and scalar transport in a round jet

Large eddy simulation of flow and scalar transport in a round jet

Turbulence and energy budget in a self-preserving round jet: direct evaluation using large eddy simulation

Development of a Nonlinear k-ε Model Incorporating Strain and Rotation Parameters for Prediction of Complex Turbulent Flows

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