Contribution to elliptic relaxation modelling of turbulent natural and mixed convection

Kenjereš, Saša; Gunarjo, S. B.; Hanjalić, K.

doi:10.1016/j.ijheatfluidflow.2005.03.007

Cited by 109 publications

(44 citation statements)

References 22 publications

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“…the ratio between the depth of the solid fuel layer by the extinction length scale. With these values, the vegetation layer can be considered as more or less optically thin [19]. Without assuming the mechanisms of heat transfer (convection or radiation) which governs the propagation of fire, we can observe that the increase in the absorption coefficient characterizing the vegetation layer contributes to improved heat transfer between the flame and the solid fuel layer and consequently to an increase in the average value of the solid fuel temperature.…”

Section: Resultsmentioning

confidence: 99%

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Impact of solid fuel particle size upon the propagation of a surface fire through a homogeneous vegetation layer

Morvan¹,

Lamorlette²

2014

Fire Saf. Sci.

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The aim of this paper is to investigate the role played by the size (thickness) of solid fuel particles upon both the heat transfer and the propagation of a surface fire through a homogeneous vegetation layer. Because all the interactions (mass, momentum, and heat transfer) between the solid fuel layer and the gas phase occur at the interface between these two media, the surface area to volume (SA/V) ratio (inversely proportional to the thickness of the solid fuel particles), which appears in the expression of the specific surface separating these two phases, must affect, more or less significantly, the fire dynamics. This problem has been studied numerically, using a multiphase formulation. Various variables, such as the temperature of the solid fuel, the temperature of the gas, the fire residence time and the heat flux by radiation and convection have been analyzed, in order to understand the role played by the SA/V upon the behaviour of the fire.

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Section: Resultsmentioning

confidence: 99%

“…In agreement with experimental observations, the ratio of scalar and velocity dissipation time (R) has been assumed to be equal to 0.5 [18,19].…”

Section: Mathematical Modelmentioning

confidence: 87%

Impact of solid fuel particle size upon the propagation of a surface fire through a homogeneous vegetation layer

Morvan¹,

Lamorlette²

2014

Fire Saf. Sci.

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“…As a consequence, several industrial computations are carried out with sophisticated Reynolds Stress Models but still use a Simple Gradient Diffusion Hypothesis for the heat fluxes, which is not satisfactory in mixed and natural convection regimes (e.g., see Kenjereš et al. [19]). The Generalized Gradient Diffusion Hypothesis (GGDH) [17] accounts for the influence of the anisotropy of the Reynolds stresses on turbulent heat fluxes, but is not sufficiently general to correctly represent buoyancy effects [14].…”

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confidence: 99%

Algebraic Modeling of the Turbulent Heat Fluxes Using the Elliptic Blending Approach—Application to Forced and Mixed Convection Regimes

Dehoux¹,

Lecocq²,

Benhamadouche³

et al. 2011

Flow Turbulence Combust

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The present paper focuses on the application of the elliptic blending approach to the modeling of turbulent heat fluxes, in order to account for the influence of solid boundaries. The analytical justification of the extension to the temperature-pressure gradient correlation term of this approach, originally applied to the velocity-pressure gradient, is given. The assumption of weak equilibrium enables the derivation of two new algebraic flux models valid down to the wall. It is shown, with both a priori tests and computations in forced and mixed convection regimes, that the predictions of the streamwise heat-flux and the temperature variance are significantly improved by the use of elliptic blending. A particular attention is devoted to the issue of the modeling of the correlation length scale involved in the elliptic blending for the heat fluxes, which is shown to have a significant influence on the predictions.

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“…An accurate prediction of the flow structure and the heat transfer in such a configuration is of great interest and despite the effort devoted (see for instance [3][4][5][6][7][8]) for an accurate turbulence modeling of this configuration, it still remains as a great challenge. This is mainly due to the complex behavior exhibit (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Parameter-free symmetry-preserving regularization modeling of a turbulent differentially heated cavity

et al. 2010

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Parameter-free symmetry-preserving regularization modeling of a turbulent differentially heated cavity Trias, F.X.; Verstappen, R.W.C.P.; Gorobets, A.; Soria, M.; Oliva, A. Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Trias, F. X., Verstappen, R. W. C. P., . Parameter-free symmetrypreserving regularization modeling of a turbulent differentially heated cavity. Computers & fluids, 39(10), 1815-1831. DOI: 10.1016/j.compfluid.2010 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. a b s t r a c tSince direct numerical simulations of buoyancy driven flows cannot be computed at high Rayleigh numbers, a dynamically less complex mathematical formulation is sought. In the quest for such a formulation, we consider regularizations (smooth approximations) of the non-linearity: the convective term is altered to reduce the production of small scales of motion by means of vortex stretching. In doing so, we propose to preserve the symmetry and conservation properties of the convective terms exactly. This requirement yielded a novel class of regularizations [Comput Fluids 2008;37:887] that restrain the convective production of smaller and smaller scales of motion in an unconditionally stable manner, meaning that the velocity cannot blow up in the energy-norm (in 2D also: enstrophy-norm). The numerical algorithm used to solve the governing equations preserves the symmetry and conservation properties too. In the present work, a criterion to determine dynamically the regularization parameter (local filter length) is proposed: it is based on the requirement that the vortex stretching must stop at the scale set by the grid. Therefore, the proposed method constitutes a parameter-free turbulence model. The resulting regularization method is tested for a 3D natural convection flow in an air-filled (Pr = 0.71) differentially heated cavity of height aspect ratio 4. Direct comparison with DNS results at Rayleigh number 6.4 Â 10 8 6 Ra 6 10 11 shows fairly good agreement even for very coarse grids. Finally, the robustness of the method is tested by performing simulations with Ra up to 10 17. A 2/7 scaling law of Nusselt number has been obtained for the investigated range of Ra.

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Contribution to elliptic relaxation modelling of turbulent natural and mixed convection

Cited by 109 publications

References 22 publications

Impact of solid fuel particle size upon the propagation of a surface fire through a homogeneous vegetation layer

Impact of solid fuel particle size upon the propagation of a surface fire through a homogeneous vegetation layer

Algebraic Modeling of the Turbulent Heat Fluxes Using the Elliptic Blending Approach—Application to Forced and Mixed Convection Regimes

Parameter-free symmetry-preserving regularization modeling of a turbulent differentially heated cavity

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