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首页> 外文期刊>International Journal of Heat and Mass Transfer >Natural convection from a circular cylinder in confined Bingham plastic fluids
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Natural convection from a circular cylinder in confined Bingham plastic fluids

机译：承压宾厄姆塑料流体中的圆柱体自然对流

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摘要

Heat transfer by laminar natural convection to Bingham plastic fluids from a heated horizontal circular cylinder in a square cavity has been investigated numerically. The governing partial differential equations describing the fluid flow and heat transfer have been solved (using the finite-element based COMSOL solver) over wide ranges of the pertinent dimensionless parameters, namely, Rayleigh number (10~3 ≤ Ra ≤ 10~5), Prandtl number (1 ≤ Pr ≤ 500) and Bingham number (0 ≤ Bn ≤ Bn_(max)) for a range of values of the ratio of the cylinder diameter to the size of the square cavity, 0.125 ≤ B ≤ 0.5. The detailed flow and temperature fields in the proximity of the heated cylinder are visualized in terms of the streamline and isotherm profiles, respectively. These also facilitate the delineation of the yielded and unyielded regions formed in different parts of the cavity. Further insights are provided in terms of the distribution of the local Nusselt number along the cylinder surface together with its average value. It is found that the average Nusselt number decreases with the increasing Bingham number up to a limiting value of the Bingham number (Bn_(max)) beyond which the average Nusselt number attains its asymptotic value, close to the pure conduction limit due to the virtually unyielding nature of the fluid. Furthermore, the influence of the aspect ratio, B, on the maximum Bingham number (Bn_(max)) and the resulting average Nusselt number has been explored extensively. It is found that as the size of the cavity increases with respect to the cylinder diameter, i.e., decreasing value of B, the both maximum Bingham number and average Nusselt number increase. On the other hand, Nusselt number shows a very weak dependence on the Prandtl number beyond that included in the definition of the Rayleigh number.
机译：对层状自然对流从方腔中受热的水平圆柱体到宾厄姆塑性流体的传热进行了数值研究。 （使用基于有限元的COMSOL求解器）已在宽范围的相关无量纲参数（即瑞利数（10〜3≤Ra≤10〜5））中求解了描述流体流动和传热的控制性偏微分方程，对于圆柱直径与方腔尺寸之比的值范围为0.125≤B≤0.5的普朗特数（1≤Pr≤500）和宾厄姆数（0≤Bn≤Bn_（max））。加热缸附近的详细流场和温度场分别通过流线和等温线图显示。这些也有助于描绘在腔的不同部分中形成的屈服和未屈服区域。在沿圆柱体表面的局部Nusselt数及其平均值的分布方面，可以提供更多的见解。已发现平均努塞尔特数随宾汉数的增加而减小，直至宾汉姆数的极限值（Bn_（max）），超过该极限值，平均努塞尔特数将达到其渐近值，接近于纯传导极限，这实际上是由于液体的坚硬性质。此外，已经广泛研究了纵横比B对最大宾厄姆数（Bn_（max））和所得平均努塞尔特数的影响。已经发现，随着腔的尺寸相对于圆柱直径的增加，即B的值减小，最大宾汉数和平均努塞尔数都增加。另一方面，除了瑞利数定义中所包含的数值以外，努塞尔数对普朗特数的依赖性非常弱。

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