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首页> 外文期刊>International Journal of Heat and Mass Transfer >From steady to unsteady horizontal gradient-driven convection at high Prandtl number
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From steady to unsteady horizontal gradient-driven convection at high Prandtl number

机译：从高Prandtl数的稳态到非稳态水平梯度驱动的对流

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摘要

A 2-D rectangular cavity subject to a horizontal temperature gradient imposed on its upper boundary induces a naturally convective flow, leading to two surprising results. First, at large Rayleigh numbers (Ra) two boundary layers appear driving the flow in such a way that heat is removed from the cold part of the fluid and released into the hot region of the fluid, generating a dynamical "heat pump". Second, a narrow region of pulsating oscillatory flow appears in the vicinity of the boundary layer which is at the vertical wall adjoining the cold edge of the upper boundary. These pulsations occur when Ra exceeds a critical value, Ra_c, and are associated with large downward and upward vertical flows that appear simultaneously near this vertical wall. The rest of the cavity is principally a "dead" cold region with weak flows. This region is the heat source of the heat pump. It occupies the main part of the cavity which progressively gets colder while the horizontal thermal boundary layer progressively gets hotter with increasing Ra. We explain the physics of these phenomena via numerical calculations that employ a spectral Cheby-shev method. It is shown, for the first time, that the curve of Ra_c versus the aspect ratio is non-monotonic. It is also shown that the fundamental frequency of the oscillations, ω, increases monotonically with the aspect ratio of the cavity that we have considered. Physical reasons are advanced to explain our observations.
机译：二维矩形腔在其上边界受到水平温度梯度的作用，会引起自然对流，从而导致两个令人惊讶的结果。首先，在较大的瑞利数（Ra）下，出现了两个边界层，以驱动流体流动的方式将热量从流体的较冷部分中除去，并释放到流体的较热区域中，从而产生了动态的“热泵”。第二，脉动振荡流的狭窄区域出现在边界层附近，该边界层在与上边界的冷边缘邻接的垂直壁处。这些脉动在Ra超过临界值Ra_c时发生，并与在此垂直壁附近同时出现的较大的向下和向上的垂直流相关。空腔的其余部分主要是流动较弱的“死”冷区。该区域是热泵的热源。它占据腔体的主要部分，随着Ra的增加，水平腔体的边界逐渐变冷，而水平热边界层逐渐变热。我们通过采用频谱Cheby-shev方法的数值计算来解释这些现象的物理现象。首次显示，Ra_c对长宽比的曲线是非单调的。还表明，振荡的基频ω随着我们所考虑的腔的长宽比而单调增加。物理上的原因可以用来解释我们的观察结果。

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  • 作者

    K.E. Uguz; G. Labrosse; R. Narayanan; F. Pigeonneau;

  • 作者单位

    Department of Chemical Engineering, University of Florida, FL 32611 Gainesville, USA;

    Departement de Physique, Universite Paris-Sud 11, 91400 Orsay Cedex, France;

    Department of Chemical Engineering, University of Florida, FL 32611 Gainesville, USA;

    Surface du Verre et Interfaces, UMR 125 CNRS/Saint-Gobain, 39 Quai Lucien Lefranc, BP 135 93303 Aubervilliers Cedex, France;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Natural convection; Spectral Chebyshev; Unsteady; High Prandtl;

    机译：自然对流;光谱切比雪夫;不稳定高普朗特;

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