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首页> 外文期刊>International journal of numerical methods for heat & fluid flow >Periodic behavior flow of three-dimensional natural convection in a titled obstructed cubical enclosure
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Periodic behavior flow of three-dimensional natural convection in a titled obstructed cubical enclosure

机译：标题为立方障碍物的三维自然对流的周期性行为流

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Purpose - The purpose of this paper is to examine numerically the three natural convection of air induced by temperature difference between a cold outer cubic enclosure and a hot inner cylinder. Simulations have been carried out for Rayleigh numbers ranging from 103 to 107 and titled angle of the enclosure from 0° to 90°. The developed mathematical model is governed by the coupled equations of continuity, momentum and energy, and is solved by finite volume method. The effects of cylinder inclination and Rayleigh number on fluid flow and heat transfer are presented. The distribution of isocontours of temperature and isosurfaces of velocity eventually reaches a steady state in the range of Rayleigh numbers between 103 and 107 for titled inclination of 90°; however, for the remaining inclinations, Rayleigh number must be in the range 103-106 to avoid unsteady state, which is manifested by the division of the area containing the maximum local heat transfer rate into three parts for a Rayleigh number equal to 107 and an inclination of 90°. We mention that instability study is not included in the present paper, which is solely devoted to three-dimensional calculations. Results also indicate that optimal average heat transfer rate is obtained for both high Rayleigh number of 106 and high inclination of 90° for the two cases of the inner cylinder and cubical enclosure. Design/methodology/approach - The manuscript deals with prediction of the three-dimensional natural convection phenomena in a cubical cavity induced by an isothermal cylinder at the center with different inclinations by simulating the flow using highly numerical methods such as finite volume method. Findings - It is found that the local Nusselt number through active walls for titled inclination set at 90°, the symmetry of the flow is conserved and the area containing the maximum heat transfer is divided into three smaller areas situated near the upper portion of the wall, taking the maximum value. That may be due to the preparation of local occurrence of instabilities and bifurcation phenomena that appear for Ra > 107, which is not included in the present paper to save journal space. It was found also that an optimal heat transfer appears when the cylinder orientation becomes vertical (a = 90°). For this inclination, buoyancy forces act upward, corresponding to an aiding situation. In addition, heat transfer rate is increasing with Rayleigh numbers, so correlations of average Nusselt through the cubical cavity and the cylinder are established as function of two parameters (Ra, a). Comparisons of the numerical results with those obtained from all correlations show good agreements. Originality/value - To the author's knowledge, studies have thus far adressed three-dimensional cuboids enclosures induced by an inner shape which the location is changed. However, no study has examined threedimensional natural convection between the inner isothermal cylinder and outer cooled cubical enclosure when the outer enclosure is tilted.
机译：目的-本文的目的是从数字上研究由冷的外部立方外壳和热的内部气缸之间的温差引起的空气的三种自然对流。对瑞利数范围从103到107，外壳的标题角从0°到90°进行了仿真。建立的数学模型由连续性，动量和能量的耦合方程式控制，并通过有限体积法求解。给出了圆柱倾角和瑞利数对流体流动和传热的影响。温度的等值线分布和速度的等值面分布最终在瑞利数为103至107的范围内达到稳定状态，标题倾角为90°。但是，对于其余的倾斜度，Rayleigh数必须在103-106范围内以避免不稳定状态，这通过将包含最大局部传热率的区域分为三个部分来实现，即Rayleigh数等于107和倾斜90°。我们提到，不稳定性研究不包括在本文中，它仅用于三维计算。结果还表明，对于内筒和立方外壳这两种情况，均获得了106的高瑞利数和90°的高倾角的最佳平均传热率。设计/方法/方法-该手稿通过使用诸如有限体积法之类的高数值方法模拟流动，来预测由等温中心处的等温圆柱体引起的立方腔体中的三维自然对流现象。发现-发现活动壁的局部Nusselt数（标称倾角设置为90°）得以保留，流的对称性得以保留，并且包含最大传热的区域被划分为三个较小的区域，位于壁的上部附近，取最大值。这可能是由于准备了Ra> 107时出现的局部不稳定性和分叉现象，为节省日记本空间而未在本白皮书中进行介绍。还发现，当圆柱体方向变为垂直方向（a = 90°）时，会出现最佳的热传递。对于这种倾斜，对应于辅助情况，浮力向上作用。此外，传热速率随着瑞利数的增加而增加，因此建立了通过两个立方腔和圆柱体的平均努塞尔相关性，这是两个参数（Ra，a）的函数。数值结果与从所有相关性获得的数值结果的比较显示出很好的一致性。独创性/价值-据作者所知，到目前为止，研究已经解决了由位置发生变化的内部形状引起的三维长方体包围。但是，没有研究检查倾斜外壳时内部等温圆柱体与外部冷却的立方外壳之间的三维自然对流。

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