Laminar natural convection boundary layers on near-horizontal plates

Ackroyd, J. A. D.

doi:10.1098/rspa.1976.0173

Cited by 22 publications

(8 citation statements)

References 16 publications

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“…In relation to analytical and/or numerical studies of the natural convective heat transfer phenomena in flat surfaces, there are the works of Ackroyd (1976), Bandrowski and Rybski (1976), Goldstein and Lau (1983), Chen et al (1986) and Wei et al (2003) as fundamental references.…”

Section: Parameters In Turbulent Simulationsmentioning

confidence: 99%

Physical–numerical parameters in turbulent simulations of natural convection on three-dimensional square plates

Júnior¹,

Scalon

Oliveira

et al. 2021

HFF

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Purpose This paper aims to study, experimentally validate and select the main physical and numerical parameters of influence in computational numerical simulations to evaluate mean heat flux by natural convection on square flat plates. Design/methodology/approach Several numerical models were built to study the influence of physical and numerical parameters about the predictions of the natural convection heat transfer rates on the surface of a flat plate with aspect ratio = 1, in isothermal conditions, turbulent regime and using the free and open-source software OpenFOAM®. The studied parameters were: boundary conditions (using or not using wall functions in properties ε, κ, νt and ω), degree of mesh refinement, refinement layers and turbulence models [κ – ε and κ – ω Shear Stress Transport (SST)]. From the comparison of the values of the mean Nusselt number, obtained from numerical simulations and literature experimental results, the authors evaluated the precision of the studied parameters, validating and selecting the most appropriate to the analyzed problem situation. Findings The validation and agreement of the numerical results could be proven with excellent precision from experimental references of the technical scientific literature. More refined meshes with refinement layers were not suitable for the studies developed. The κ – ε and κ – ω SST turbulence models, in meshes without refinement layers, proved to be equivalent. Whether or not to use wall functions in turbulent boundary conditions proved to be irrelevant as to the accuracy of results for the problem situation studied. Practical implications Use of the physical and numerical parameters is studied and validated for various applications in natural convection heat transfer of technology and industry areas. Social implications Use of free and open-source software as a research tool in the Computational Fluid Dynamics (CFD) area, especially in conditions without large financial resources or state-of-the-art infrastructure. Originality/value To the best of the authors’ knowledge, this work is yet not available in existing literature.

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Section: Parameters In Turbulent Simulationsmentioning

confidence: 99%

Physical–numerical parameters in turbulent simulations of natural convection on three-dimensional square plates

Júnior¹,

Scalon

Oliveira

et al. 2021

HFF

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“…As classic references and basic theoretical rationale on the analytical and numerical study of natural convection in rectangular flat plates, the works of Ackroyd (1976), Bandrowski and Rybski (1976), Goldstein and Lau (1983), Chen et al (1986) and Wei et al (2003).…”

Section: Introductionmentioning

confidence: 99%

Physical–numerical parameters in laminar simulations of natural convection on three-dimensional square plates

Júnior¹,

Scalon

Oliveira

2021

HFF

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Purpose The purpose of this study is to analyze the influence of the main physical–numerical parameters in the computational evaluation of natural convection heat transfer rates in isothermal flat square plates in the laminar regime. Moreover by experimentally validate the results of the numerical models and define the best parameter settings for the problem situation studied. Design/methodology/approach The present work is an extension of the study by Verderio Junior et al. (2021), differing in the modeling, results analysis and conclusions for the laminar flow regime with Rade=1×105. The analysis of the influence and precision of the physical–numerical parameters: boundary conditions, degree of mesh refinement, refinement layers and κ – ω SST and κ – ε turbulence models, occurred from the results from 48 numerical models, which were simulated using the OpenFOAM® software. Comparing the experimental mean Nusselt number with the numerical values obtained in the simulations and the analysis of the relative errors were used in the evaluation of the advantages, restrictions and selection of the most adequate parameters to the studied problem situation. Findings The numerical results of the simulations were validated, with excellent precision, from the experimental reference by Kitamura et al. (2015). The application of the κ – ω SST and κ – ε turbulence models and the boundary conditions (with and without wall functions) were also physically validated. The use of the κ – ω SST and κ – ε turbulence models, in terms of cost-benefit and precision, proved to be inefficient in the problem situation studied. Simulations without turbulence models proved to be the best option for the physical model for the studies developed. The use of refinement layers, especially in applications with wall functions and turbulence models, proved unfeasible. Practical implications Use of the physical–numerical parameters studied and validated, and application of the modeling and analysis methodology developed in projects and optimizations of natural convection thermal systems in a laminar flow regime. Just like, reduce costs and the dependence on the construction of experimental apparatus to obtain experimental results and in the numerical-experimental validation process. Social implications Exclusive use of free and open-source computational tools as an alternative to feasible research in the computational fluid dynamics area in conditions of budget constraints and lack of higher value-added infrastructure, with applicability in the academic and industrial areas. Originality/value The results and discussions presented are original and new for the applied study of laminar natural convection in isothermal flat plate, with analysis and validation of the main physical and numerical influence parameters.

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“…While they observed flow partitioning through collision lines for the boundary layer along the plate edges for each of the planforms, in the case of the circular plate, they found radially accelerating flow from the edges, which then transitioned into a billowing plume at the center. Ackroyd [7] investigated the edge flows and fluid property variations for rectangular horizontal plates and Al-Arabi and El-Riedy [8] conducted further heat transfer studies on plates of various shapes, and observed both edge and corner effects, whereas Garcia-Ybarra and Trevino [9] analyzed the thermal diffusion effects of hydrogen-air mixtures within the development of a boundary layer on a hot flat plate. Heat transfer experimental studies have also been performed circular cylindrical conduit [12], on finned tubes to determine the effect on refrigeration efficiency [13], and basic analysis on a heated cylinder [18].…”

Section: Figure 1 Hot Surface Flow Mechanismmentioning

confidence: 99%

The fluid thermal field over a flat heated disk

Landers¹,

Disimile²,

Toy³

2017

IJHT

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Numerous fires in the aviation community are typically initiated and sustained when a flammable fluid leaks onto a heated surface sometimes resulting in a catastrophic event. Due to the complex fluid thermal nature of these phenomena a two-prong effort was undertaken. Within this phase of the effort the focus is to provide insight into the fluid dynamic and thermal nature of a flow field induced by a heated surface. To this end the current work discusses the temperature and velocity fields immediately above a circular flat plate 20 cm diameter and which was heated to temperatures between 150 ℃ and 550 ℃. Both Schlieren and laser light sheet methodologies had been used to acquire data for qualitative and quantitative examination of the flow field. It has been found that the streamlines referred to as collision lines which emanate from the edge of the plate point radially inward towards the plates center. These lines connect and form cellular structures adjacent to the plates' surface. These cell-like structures appear to be reminiscent of Rayleigh Bernard type cells of either 5 or 6 sided constructions. In addition, at certain surface temperatures, pool boiling of the fluid is initiated; however, at even higher temperatures film boiling typically occurs which is thought to lead to ignition and flame propagation. The results concluded that as the distance increases from the plate the velocity of the vortical structures increases while the temperature decreases.

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Laminar natural convection boundary layers on near-horizontal plates

Cited by 22 publications

References 16 publications

Physical–numerical parameters in turbulent simulations of natural convection on three-dimensional square plates

Physical–numerical parameters in turbulent simulations of natural convection on three-dimensional square plates

Physical–numerical parameters in laminar simulations of natural convection on three-dimensional square plates

The fluid thermal field over a flat heated disk

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