Validation of Turbulence Models for Analysis of a Single-Phase Turbulent Natural Convection

Unsteady natural convection in a nonuniformly stratified, finite depth layer of water heated from below has been studied. Laboratory experiments were performed using the Mach-Zehnder interferometer as a diagnostic tool for measuring temperature. A shadowgraph technique was used for flow visualization. A simple thermal and a more detailed two-differential equation k–ε turbulence models are used to predict the dynamics of mixed layer which develops when the thermally stratified fluid is heated from below. The thermal model predictions for the mixed layer height agreed to within 5 percent and the mixed layer temperature to within 15 percent of the experimental data obtained in controlled laboratory experiments. Even better agreement between data and predictions were obtained with the k–ε turbulence model. The entrainment processes at the interface between the mixed layer and the stable region as well as turbulence in the layer must be better understood for more realistic modeling of turbulent natural convection in nonuniformly stratified fluids.

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Computational fluid dynamics and experimental study of turbulent natural convection with surface thermal radiation in a cubic enclosure

International Journal of Modern Physics C ◽

10.1142/s0129183120500655 ◽

2020 ◽

Vol 31 (05) ◽

pp. 2050065

Author(s):

J. M. A. Navarro ◽

J. F. Hinojosa ◽

I. Hernández-López

Keyword(s):

Heat Transfer ◽

Fluid Dynamics ◽

Experimental Data ◽

Experimental Study ◽

Computational Fluid Dynamics ◽

Natural Convection ◽

Thermal Radiation ◽

Turbulence Models ◽

Numerical Results ◽

Turbulent Natural Convection

This paper reports a computational fluid dynamics and experimental study to analyze the effect of surface thermal radiation on the turbulent natural convection in a closed cubic cavity. Experimental and numerical results are compared for low and high wall emissivities. Experimental temperature profiles were obtained at six different depths and heights consisting of 14 thermocouples each. Several turbulence models were evaluated against experimental data. It was found that renormalized [Formula: see text]-[Formula: see text] and standard [Formula: see text]-[Formula: see text] turbulence models present the best agreement with the experimental data for emissivities of walls of 0.98 and 0.03, respectively. Thus, the numerical results of temperature fields and flow patterns were obtained with these models. From the results, it was found that the effect of thermal radiation on experimental heat transfer coefficients is significantly, increased between 48.7% ([Formula: see text]) and 50.16% ([Formula: see text]), when the emissivity of the walls increases from 0.03 to 0.98. Therefore, the radiative exchange should not be neglected in heat transfer calculations in cubic enclosures, even if the temperature difference between heated wall and cold wall is relatively small (between 15 and 30[Formula: see text]K).

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Comparative study of standardk–ε andk–ω turbulence models by giving an analysis of turbulent natural convection in an enclosure

EPJ Web of Conferences ◽

10.1051/epjconf/20158201057 ◽

2015 ◽

Vol 82 ◽

pp. 01057 ◽

Cited By ~ 4

Author(s):

Igor Miroshnichenko ◽

Mikhail Sheremet

Keyword(s):

Natural Convection ◽

Comparative Study ◽

Turbulence Models ◽

Turbulent Natural Convection

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Computational Simulation of Turbulent Natural Convection in a Volumetrically Heated Square Cavity

Volume 3: Nuclear Safety and Security; Codes, Standards, Licensing and Regulatory Issues; Computational Fluid Dynamics and Coupled Codes ◽

10.1115/icone21-15486 ◽

2013 ◽

Cited By ~ 1

Author(s):

Camila Braga Vieira ◽

Bojan Niceno ◽

Jian Su

Keyword(s):

Natural Convection ◽

Turbulence Modeling ◽

Stokes Equations ◽

Computational Simulation ◽

Turbulence Models ◽

Navier Stokes ◽

Oxide Material ◽

Square Cavity ◽

Navier Stokes Equations ◽

Turbulent Natural Convection

This work aimed to analyze the turbulent natural convection in a volumetrically heated fluid with Prandtl number equal to 0.6, representing the oxide material layer of a corium. Four turbulence models were scrutinized in order to select the most appropriate one for turbulence modeling based on Reynolds Averaged Navier-Stokes equations (RANS) of natural convection in a molten core. The turbulence models scrutinized are the standard k-ε, Shear Stress Transport (SST), low-Reynolds-k-ε (Launder-Sharma) and also an elliptic blending model ν2-f. The simulations were carried out in a square cavity with isothermal walls, for Rayleigh numbers (Ra) ranging from 109 to 1011. The numerical simulations, performed in an open-source of Computational Fluid Dynamics (CFD) - OpenFOAM (Open Field Operation and Manipulation), provided outcomes of average Nusselt number as function of Ra number, which were in a reasonable agreement with an experimental correlation and other authors’ simulations. It was also possible to observe the limitations and robustness of each model analyzed, enabling to conclude that the most adequate turbulence models for the present physical problem were SST and ν2-f.

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