Intermittent patterns in mixed convection

Ouazzani, M. T.; Mojtabi, Abdelkader

doi:10.1007/bf00849272

Cited by 26 publications

(10 citation statements)

References 11 publications

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“…When investigating the nonlinear behavior of the PBF, the structure of the flow becomes much more complex. Experimental works by Ouazzani et al 14,16,17 or by Chiu and Rosenberger, 9 recent 3-D numerical simulations 15,18 and studies based on a weakly nonlinear Ginzburg-Landau model 19,20 have shown that the transition R Ќ -R ʈ is not as sharp as it is represented in Fig. 1.…”

Section: Introductionmentioning

confidence: 91%

Two-dimensional numerical analysis of the Poiseuille–Bénard flow in a rectangular channel heated from below

1997

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The Poiseuille-Bénard flow ͑PBF͒ is studied by a two-dimensional numerical simulation for a Prandtl number equal to 6.4 ͑that of water at 23°C͒ and for a wide range of Rayleigh ͑Ra͒ and Reynolds ͑Re͒ numbers: Raр6000 and Reр3. The two observed flow configurations are ͑1͒ thermally stratified Poiseuille flow and ͑2͒ thermoconvective transversal rolls superimposed to the basic Poiseuille flow. The time evolution of the velocity components, the spatial development of the transversal rolls, their frequency, wavelength and velocity, the Nusselt number, together with the stability map in the Ra-Re plane, are studied in detail. Whenever possible, quantitative comparisons are made with published results: most of the experimental data, based on laser-Doppler anemometry ͑LDA͒, are recovered with amazing accuracy; a good agreement with results of convective stability deduced from a weakly nonlinear Ginzburg-Landau theory is also obtained.

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Section: Introductionmentioning

confidence: 91%

Two-dimensional numerical analysis of the Poiseuille–Bénard flow in a rectangular channel heated from below

1997

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“…Many works on mixed convection in pure fluid are available since at least one decade [1][2][3][4][5][6][7], but only a few deal with mixed convection in binary fluid with Soret effect [8] (i.e. a mass flux induced by a temperature gradient).…”

Section: Abridged English Versionmentioning

confidence: 99%

“…L'étude de la convection mixte en fluide monoconstituant a fait l'objet de nombreux travaux durant les dix dernières années aussi bien du point de vue théorique (étude de stabilité linéaire, faiblement non-linéaire [1,2]), que du point de vue numérique (étude 2D pour l'analyse des rouleaux transversaux [3,4] et 3D pour l'analyse des rouleaux longitudinaux [5]) et d'un point de vue expérimental (visualisation par plan laser et anémométrie laser [6,7]).…”

Section: Introductionunclassified

Convection mixte en fluide binaire avec effet Soret : étude analytique de la transition vers les rouleaux transversaux 2D

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Charrier-Mojtabi

Azaïez

et al. 2004

Comptes Rendus. Mécanique

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Dans cette Note on étudie la convection mixte en fluide binaire avec effet Soret en canal rectangulaire chauffé par le bas. On s'intéresse plus particulièrement à la transition vers les rouleaux transversaux 2D qui apparaissent pour de faibles nombres de Reynolds et de Rayleigh. L'analyse de stabilité linéaire de l'écoulement de Poiseuille, stratifié linéairement en température et concentration, montre l'influence du facteur de séparation sur le nombre de Rayleigh critique de la transition vers les rouleaux transversaux. A faible nombre de Reynolds, on met en évidence la présence de rouleaux se propageant dans le même sens ou en sens inverse de l'écoulement moyen. On montre également que dans ces conditions, la fréquence de propagation des rouleaux correspond à la somme des fréquences obtenues en convection mixte thermique et en convection naturelle thermosolutale. AbstractMixed convection in binary fluid with Soret effect: study of the transition towards transverse 2D rolls. This Note deals with mixed convection in binary fluid with Soret effect in a rectangular duct heated from below. In particular, we study the transition towards transverse 2D rolls appearing at low Reynolds and Rayleigh numbers. The linear stability analysis of Poiseuille flow, with linearly stratified temperature and concentration fields, shows the influence of the separation ratio on the critical Rayleigh number at the transition towards the transversal 2D convective patterns. It highlights the presence, at low Reynolds numbers, of propagating transverse rolls in the downwards as well as in the upwards direction. Finally, we point out that, under these conditions, the propagating frequency of the rolls is the sum of two well defined frequencies: the first related to the Reynolds, the second to the separation ratio.

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“…Later on, Luijkx et al 9 have demonstrated the existence of transverse rolls parallel to the flow direction for which the critical Rayleigh number increases when Reynolds number increases. Several experimental and numerical investigations were carried out to determine the conditions of transverse roll onset in a rectangular channel 3,10,11 . They also proved that the critical Rayleigh number of the appearance of the transverse rolls depends on the Prandtl number and the aspect ratio of the channel.…”

Section: Introductionmentioning

confidence: 97%

Linear stability analysis of mixed convection flow in a horizontal channel filled with nanofluids

et al. 2020

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The convective instability driven by buoyancy in the Poiseuille-Rayleigh-Bénard flow through two infinite parallel horizontal plates filled with nanofluids is investigated using linear stability analysis. We considered water-based nanofluids with different volume fractions of aluminum (Al O 2 3 ) and silver (Ag) nanoparticles. A spectral collocation method founded on Chebyshev polynomials is implemented and the obtained algebraic eigenvalue problem is solved. In this study, we have numerically determined the critical Rayleigh number of the onset of longitudinal and transversal rolls and the results are represented in the form of marginal stability curves. Critical wave numbers that describe the size of convective cells in the flow are also presented, analyzed, and compared with those of the Poiseuille-Rayleigh-Bénard flow without nanoparticles. The effects of the type and nanoparticle volume fractions on the onset of both longitudinal and transversal rolls are investigated. K E Y W O R D S mixed convection, nanofluids, Poiseuille-Rayleigh-Bénard, thermoconvective instabilities

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Intermittent patterns in mixed convection

Cited by 26 publications

References 11 publications

Two-dimensional numerical analysis of the Poiseuille–Bénard flow in a rectangular channel heated from below

Two-dimensional numerical analysis of the Poiseuille–Bénard flow in a rectangular channel heated from below

Convection mixte en fluide binaire avec effet Soret : étude analytique de la transition vers les rouleaux transversaux 2D

Linear stability analysis of mixed convection flow in a horizontal channel filled with nanofluids

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