Transitions in a Poiseuille-Rayleigh-Bénard flow in a vertical slender long duct

IF 2.5 3区 工程技术 Q2 MECHANICS
Raúl Rechtman, Alejandra García-Morales, Guadalupe Huelsz
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For <span><math><mrow><mi>R</mi><msub><mrow><mi>a</mi></mrow><mrow><mi>c</mi></mrow></msub><mo>&lt;</mo><mi>R</mi><mi>a</mi><mo>≤</mo><mn>2</mn><mo>.</mo><mn>0</mn><mspace></mspace><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> with <span><math><mrow><mi>R</mi><msub><mrow><mi>a</mi></mrow><mrow><mi>c</mi></mrow></msub></mrow></math></span> the critical Rayleigh number for thermal convection, there are two transitions at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mn>0</mn></mrow></msub><mrow><mo>(</mo><mi>R</mi><mi>a</mi><mo>)</mo></mrow></mrow></math></span> and <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>C</mi><mi>P</mi></mrow></msub><mrow><mo>(</mo><mi>R</mi><mi>a</mi><mo>)</mo></mrow></mrow></math></span>, <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>&lt;</mo><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>C</mi><mi>P</mi></mrow></msub></mrow></math></span>. The first transition at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span> has a sharp decrease in the average Nusselt number and for <span><math><mrow><mn>0</mn><mo>&lt;</mo><mi>R</mi><mi>e</mi><mo>&lt;</mo><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span> the temperature difference between the horizontal walls is more important than the pressure gradient. The second transition at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>C</mi><mi>P</mi></mrow></msub></mrow></math></span> marks the appearance of a conductive Poiseuille flow with no thermal convection. For <span><math><mrow><mn>1</mn><mo>.</mo><mn>0</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> ¡ <span><math><mrow><mi>R</mi><mi>a</mi></mrow></math></span> there is a third transition at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>M</mi></mrow></msub></mrow></math></span>, <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>&lt;</mo><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>M</mi></mrow></msub><mo>&lt;</mo><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>C</mi><mi>P</mi></mrow></msub></mrow></math></span>. For <span><math><mrow><mi>R</mi><mi>a</mi><mo>&lt;</mo></mrow></math></span> <span><math><mrow><mn>1</mn><mo>.</mo><mn>0</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> and <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>&lt;</mo><mi>R</mi><mi>e</mi><mo>&lt;</mo><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>C</mi><mi>P</mi></mrow></msub></mrow></math></span>, and for <span><math><mrow><mn>1</mn><mo>.</mo><mn>0</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> <span><math><mrow><mo>&lt;</mo><mi>R</mi><mi>a</mi></mrow></math></span> and <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>M</mi></mrow></msub><mo>&lt;</mo><mi>R</mi><mi>e</mi><mo>&lt;</mo><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>C</mi><mi>P</mi></mrow></msub></mrow></math></span>, the pressure gradient dominates over the pressure gradient. Both the temperature difference and the pressure gradient are important for <span><math><mrow><mn>1</mn><mo>.</mo><mn>0</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup><mo>&lt;</mo><mi>R</mi><mi>a</mi></mrow></math></span> and <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>&lt;</mo><mi>R</mi><mi>e</mi><mo>&lt;</mo><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>M</mi></mrow></msub></mrow></math></span> with an appreciable decrease of the average Nusselt number at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span> and <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>M</mi></mrow></msub></mrow></math></span>.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"105 ","pages":"Pages 306-312"},"PeriodicalIF":2.5000,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"European Journal of Mechanics B-fluids","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0997754624000219","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MECHANICS","Score":null,"Total":0}
引用次数: 0

Abstract

The flow of air inside a vertical slender long duct with a temperature difference between the horizontal walls characterized by the Rayleigh number Ra and a pressure gradient in the horizontal direction characterized by the Reynolds number Re is studied using the lattice Boltzmann method. In this case, the longitudinal rolls found in ducts with a width larger than the height cannot develop and the flow remains quasi-two-dimensional. Therefore, a two-dimensional approach is used, considering periodic boundary conditions on the vertical walls. For Rac<Ra2.0×105 with Rac the critical Rayleigh number for thermal convection, there are two transitions at Re0(Ra) and ReCP(Ra), Re0<ReCP. The first transition at Re0 has a sharp decrease in the average Nusselt number and for 0<Re<Re0 the temperature difference between the horizontal walls is more important than the pressure gradient. The second transition at ReCP marks the appearance of a conductive Poiseuille flow with no thermal convection. For 1.0×105 ¡ Ra there is a third transition at ReM, Re0<ReM<ReCP. For Ra< 1.0×105 and Re0<Re<ReCP, and for 1.0×105 <Ra and ReM<Re<ReCP, the pressure gradient dominates over the pressure gradient. Both the temperature difference and the pressure gradient are important for 1.0×105<Ra and Re0<Re<ReM with an appreciable decrease of the average Nusselt number at Re0 and ReM.

垂直细长管道中波伊-雷利-贝纳尔流的转变
采用格子波尔兹曼法研究了垂直细长管道内的气流,其水平壁之间的温差以雷利数 Ra 为特征,水平方向上的压力梯度以雷诺数 Re 为特征。在这种情况下,在宽度大于高度的管道中无法形成纵向滚动,流动仍然是准二维的。因此,考虑到垂直壁上的周期性边界条件,采用了二维方法。当 Rac<Ra≤2.0×105 时(Rac 为热对流的临界瑞利数),在 Re0(Ra)和 ReCP(Ra), Re0<ReCP 处有两个过渡。在 Re0 处的第一个过渡阶段,平均努塞尔特数急剧下降,对于 0<Re<Re0,水平壁之间的温度差比压力梯度更重要。ReCP 处的第二个转变标志着出现了无热对流的传导性普瓦赛流。对于 1.0×105 ¡ Ra,ReM 处出现第三个过渡,即 Re0<ReM<ReCP。对于 Ra< 1.0×105 和 Re0<Re<ReCP,以及对于 1.0×105<Ra 和 ReM<Re<ReCP,压力梯度占主导地位。对于 1.0×105 ¡ Ra 和 Re0<Re<ReM,温差和压力梯度都很重要,在 Re0 和 ReM 时平均努塞尔特数明显下降。
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来源期刊
CiteScore
5.90
自引率
3.80%
发文量
127
审稿时长
58 days
期刊介绍: The European Journal of Mechanics - B/Fluids publishes papers in all fields of fluid mechanics. Although investigations in well-established areas are within the scope of the journal, recent developments and innovative ideas are particularly welcome. Theoretical, computational and experimental papers are equally welcome. Mathematical methods, be they deterministic or stochastic, analytical or numerical, will be accepted provided they serve to clarify some identifiable problems in fluid mechanics, and provided the significance of results is explained. Similarly, experimental papers must add physical insight in to the understanding of fluid mechanics.
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