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首页> 外文期刊>Applied Mathematical Modelling >Buoyancy-assisted flow of yield stress fluids past a cylinder: Effect of shape and channel confinement
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Buoyancy-assisted flow of yield stress fluids past a cylinder: Effect of shape and channel confinement

机译：浮力辅助的屈服应力流体流过圆柱体：形状和通道限制的影响

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The aiding-buoyancy mixed convection heat transfer in Bingham plastic fluids from an isothermal cylinder of elliptical and circular shape in a vertical adiabatic channel is numerically investigated. For a fixed shape of the elliptical cylinder E=2 (ratio of major to minor axes), the effect of confinement is studied for three values of blockage ratio, B, defined as the ratio of the channel width to the circumference of the cylinder/pi, as 6.5, 2.17 and 1.3. In order to delineate the role of cross-section of the cylinder, results are also presented here for a circular cylinder of the same heat transfer area as the elliptical cylinder. The results presented herein span the range of conditions as: Bingham number, 0 <= Bn <= 100, Reynolds number, 1 <= Re <= 40, and Prandtl number, 1 <= Pr <= 100 over the range of Richardson number Ri = 0 (pure forced convection) to Ri= 10. Extensive results on drag coefficient, local and surface averaged values of the Nusselt number and yield surfaces are presented herein to elucidate the combined effects of buoyancy, blockage ratio and fluid yield stress. The morphology of the yield surfaces shows that the unyielded plug regions formed upstream and downstream of the cylinder grow faster at low Reynolds numbers with the increasing yield stress effects under the weak buoyancy forces, i.e., small values of Grashof or Richardson number. The heat transfer enhancement is observed with the increasing channel-confinement due to the sharpening of the temperature gradients near the surface of the cylinder. The average Nusselt number shows a positive dependence on the Reynolds number, Prandtl number and Richardson number irrespective of the shape of the cylinder or the type of fluid. By employing the modified definitions of the dimensionless parameters (based on the two choices of the overall effective fluid velocity), predictive correlations have been established for estimating the value of the average Nusselt number in a new application. (C) 2019 Elsevier Inc. All rights reserved.
机译：对宾汉塑性流体在垂直绝热通道中椭圆和圆形等温圆柱体中辅助浮力混合对流换热进行了数值研究。对于椭圆形圆柱体的固定形状E = 2（长轴与短轴之比），研究了三种堵塞率值B的限制效果，堵塞率B定义为通道宽度与圆柱体周长/ pi，分别为6.5、2.17和1.3。为了描述圆柱体的横截面作用，此处还给出了与椭圆形圆柱体具有相同传热面积的圆柱体的结果。本文介绍的结果涵盖以下条件范围：在理查森数范围内，宾厄姆数，0 <= Bn <= 100，雷诺数，1 <= Re <= 40和普朗特数，1 <= Pr <= 100 Ri = 0（纯对流）到Ri =10。本文介绍了阻力系数，努塞尔特数和屈服面的局部和表面平均值的广泛结果，以阐明浮力，阻塞率和流体屈服应力的综合影响。屈服面的形态表明，在低雷诺数下，圆柱的上游和下游形成的未屈服的塞子区域随着在弱浮力即较小的Grashof或Richardson数下的屈服应力效应的增加而在较低的雷诺数下增长更快。由于圆柱表面附近温度梯度的锐化，随着通道约束的增加，观察到了传热的增强。无论圆柱体的形状或流体的类型如何，平均努塞尔数都对雷诺数，普朗特数和理查森数呈正相关关系。通过使用无量纲参数的修改定义（基于总有效流体速度的两个选择），建立了预测相关性，以估计新应用中的平均努塞尔数值。 （C）2019 Elsevier Inc.保留所有权利。

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