Bingham塑性流体中受热圆柱体的涡脱落与传热
Vortex shedding and heat transfer from a heated circular cylinder in Bingham plastic fluids
AI总结：
本文数值研究了Bingham塑性流体中受热圆柱体的涡脱落与传热特性，系统分析了Re、Pr和Bn的影响，揭示了亚临界分岔导致的阻力与传热突跳，并建立了平均Nusselt数与Bingham数之间的类Carreau-Yasuda黏度模型关系。
摘要：
本研究数值研究了浸没在Bingham塑性流体中的受热圆柱体的涡脱落与传热特性。评估了三个参数的影响，即：(i) 塑性Reynolds数（$10 \leq Re \leq 180$），(ii) Prandtl数（$1\leq Pr \leq 100$），以及(iii) Bingham数（$0 \leq Bn \leq 10,000$）。采用Navier-Stokes方程和能量方程来描述流动与传热，并结合Papanastasiou正则化来处理Bingham塑性流体的不连续黏度特性。为阐明流体屈服应力对流动结构的影响，本研究对流动转捩、流线、剪切速率和速度分布、屈服/未屈服区域的形态以及阻力系数（$C_d$）提供了全面的认识。此外，还分析了温度分布、沿圆柱表面的局部Nusselt数（$\overline{Nu_{local}}$）以及圆柱上的平均Nusselt数（$\overline{Nu}$）。结果表明，Bingham流体绕圆柱的流动转捩依赖于外部扰动，表现出亚临界分岔行为。这导致在临界Bingham数$Bn_c$附近，$\overline{Cd}$-$Bn$曲线和$\overline{Nu}$-$Bn$曲线出现突跳。此外，传热性能取决于不同$Bn$范围内边界层中剪切应变率的不同分布。观察到$\overline{Nu}$与$Bn$能很好地符合类Carreau-Yasuda非牛顿黏度模型。本研究加深了对Bingham塑性流体中涡脱落与传热行为的理解。
英文摘要：
The present study numerically investigates the vortex shedding and heat transfer characteristics of a heated circular cylinder immersed in Bingham plastic fluids.The effects of three parameters, i.e., (i) plastic Reynolds number ($10 \leq Re \leq 180$), (ii) Prandtl number ($1\leq Pr \leq 100$), and (iii) the Bingham number ($0 \leq Bn \leq 10,000$), are evaluated. The Navier-Stokes and energy equations for flow and heat transfer are adopted, along with the incorporation of the Papanastasiou regularization to address the discontinuous-viscosity characteristics of Bingham plastic fluids. To illustrate the impact of fluid yield stress on the flow structure, the study provides comprehensive insights into flow transition, streamlines, shear rate and velocity distributions, the morphology of yielded/unyielded regions, and the drag coefficient ($C_d$). Additionally, the temperature distribution, the local Nusselt number ($\overline{Nu_{local}}$) along the cylinder, and the average Nusselt number on the cylinder ($\overline{Nu}$) are analyzed. The results indicate that the flow transition of Bingham fluids over a circular cylinder is dependent on external disturbances, exhibiting subcritical bifurcation behavior. This leads to abrupt jumps in the $\overline{Cd}$ - $Bn$ curve and the $\overline{Nu}$ - $Bn$ curve near the critical Bingham number $Bn_c$. Furthermore, the heat transfer performance is contingent upon the different distribution of shear strain rate in the boundary layer across various $Bn$ ranges. It is observed that $\overline{Nu}$ and $Bn$ fits well with the Carreau-Yasuda-like non-Newtonian viscosity model. This investigation enhances the understanding of the vortex shedding and heat transfer behaviors in Bingham plastic fluids.
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