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首页> 外文期刊>International Journal of Heat and Mass Transfer >Momentum and heat transfer characteristics of a semi-circular cylinder immersed in power-law fluids in the steady flow regime
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Momentum and heat transfer characteristics of a semi-circular cylinder immersed in power-law fluids in the steady flow regime

机译：稳态流动状态下浸没在幂律流体中的半圆柱的动量和传热特性

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摘要

The continuity, momentum and energy equations describing the flow and heat transfer of power-law fluids over a semi-circular cylinder have been solved numerically in the two-dimensional steady flow regime. The influence of the Reynolds number (Re), Prandtl number (Pr) and power-law index (n) on the local and global flow and heat characteristics have been studied over wide ranges of conditions as follows: 0.01≤Re < 30, 1≤Pr ≤100 and 0.2≤n ≤1.8. The variation of drag coefficient and Nusselt number with the Reynolds number, Prandtl number and power-law index is shown over the aforementioned ranges of conditions. In addition, streamline and isotherm profiles along with the recirculation length and distribution of pressure coefficient and Nusselt number over the surface of the semi-circular cylinder are also presented to gain further insights into the nature of the underlying kinematics. The wake size (recirculation length) shows almost linear dependence on the Reynolds number (Re≥1) for all values of power-law index studied herein. The drag values show the classical inverse variation with the Reynolds number, especially for shear-thinning fluids at low Reynolds numbers. The point of maximum pressure coefficient is found slightly displaced from the front stagnation point for highly shearthinning fluids, whereas for shear-thickening and Newtonian fluids, it coincides with the front stagnation point. For fixed values of the Prandtl number and Reynolds number, the rate of heat transfer decreases with the gradual increase in power-law index; this effect is particularly striking at high Prandtl numbers due to the thinning of the thermal boundary layer. Conversely, as expected, shear-thinning behavior facilitates heat transfer and shear-thickening impedes it. The effect of power-law index on both momentum and heat-transfer characteristics is seen to be appreciable at low Reynolds numbers and it gradually diminishes with the increasing Reynolds number.
机译：在二维稳态流态下，用数值方法求解了描述幂律流体在半圆柱体上的流动和传热的连续性，动量和能量方程。雷诺数（Re），普朗特数（Pr）和幂律指数（n）对局部和全局流动和热特性的影响已在以下各种条件下进行了研究：0.01≤Re<30，1 ≤Pr≤100和0.2≤n≤1.8。在上述条件范围内，示出了阻力系数和努塞尔数随雷诺数，普朗特数和幂律指数的变化。此外，还介绍了流线和等温线轮廓以及在半圆形圆柱体表面上的再循环长度，压力系数和Nusselt数的分布，以进一步了解基本运动学的性质。对于本文研究的幂律指数的所有值，尾流尺寸（再循环长度）几乎都与雷诺数（Re≥1）呈线性关系。阻力值显示出随雷诺数的经典逆变化，特别是对于低雷诺数的剪切稀化流体。对于高剪切稀化流体，发现最大压力系数点与前停滞点略有偏离，而对于剪切增稠和牛顿流体，则与前停滞点重合。对于普朗特数和雷诺数的固定值，传热速率随着幂律指数的逐渐降低而降低；由于热边界层变薄，在高Prandtl数下，这种影响尤为明显。相反，如预期的那样，剪切稀化行为促进了传热，而剪切稠化则阻碍了传热。在低雷诺数下，幂律指数对动量和传热特性的影响被认为是明显的，并且随着雷诺数的增加逐渐减小。

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