Flow Regimes and Types of Solid Obstacle Surface Roughness in Turbulent Heat Transfer Inside Periodic Porous Media
Flow Regimes and Types of Solid Obstacle Surface Roughness in Turbulent Heat Transfer Inside Periodic Porous Media
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DOI：
10.1007/s11242-023-01978-6
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发表时间：
2022-10
影响因子：
2.7
通讯作者：
V. Srikanth;Dylan Peverall;A. Kuznetsov
中科院分区：
文献类型：
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作者：
V. Srikanth;Dylan Peverall;A. Kuznetsov
固体障碍物表面粗糙度在多孔介质湍流对流中的作用尚未得到很好的理解，尽管它在许多应用中经常用于增强传热。本文的重点是系统研究多孔介质中固体障碍物表面粗糙度对微尺度流动物理的影响，并报道其对宏观尺度阻力和努塞尔数的影响。采用可实现的k-ε模型，对由方形圆柱体组成的周期性多孔介质的流场进行了数值模拟。根据表面粗糙度、颗粒高度确定了两种流动形式——细粗糙度和粗粗糙度。细粗糙区粗糙度颗粒的影响仅限于固体障碍物表面附近的近壁面边界层。在粗糙粗糙状态下，粗糙颗粒改变了多孔介质整个孔隙空间的微尺度流场。在细粗糙度条件下，粗糙的固体障碍物向多孔介质内流体传递的热量小于光滑的固体障碍物。在粗糙的粗糙状态下，从粗糙的固体障碍物到多孔介质内部的流体的传热增强。总阻力减少也观察到在细粗糙制度最小的粗糙度颗粒高度。表面粗糙度颗粒间距决定了固体障碍物表面被再循环、再附着和停滞流覆盖的面积的分数。随着粗糙度颗粒间距的增加，传热率的增加是由于再附着流覆盖的表面积增加，而传热率的降低是由于固体障碍物表面粗糙度颗粒的减少。减小孔隙率和增大雷诺数可以放大表面粗糙度对微尺度流动的影响。结果表明，如果能够克服阻力的增加，多孔介质中的传热可以得到加强。结果还表明，由于腐蚀而经常遇到的细小粗糙状态不利于多孔介质的传热性能。
The role of solid obstacle surface roughness in turbulent convection in porous media is not well understood, even though it is frequently used for heat transfer enhancement in many applications. The focus of this paper is to systematically study the influence of solid obstacle surface roughness in porous media on the microscale flow physics and report its effect on macroscale drag and Nusselt number. The Reynolds-averaged flow field is numerically simulated using the realizablek-ε model for a flow through a periodic porous medium consisting of an in-line arrangement of square cylinders with square roughness particles on the cylinder surface. Two flow regimes are identified with respect to the surface roughness particle height—fine and coarse roughness regimes. The effect of the roughness particles in the fine roughness regime is limited to the near-wall boundary layer around the solid obstacle surface. In the coarse roughness regime, the roughness particles modify the microscale flow field in the entire pore space of the porous medium. In the fine roughness regime, the heat transfer from the rough solid obstacles to the fluid inside the porous medium is less than that from a smooth solid obstacle. In the coarse roughness regime, there is an enhancement in the heat transfer from the rough solid obstacle to the fluid inside the porous medium. Total drag reduction is also observed in the fine roughness regime for the smallest roughness particle height. The surface roughness particle spacing determines the fractional area of the solid obstacle surface covered by recirculating, reattached, and stagnating flow. As the roughness particle spacing increases, there are two competing factors for the heat transfer rate—increase due to more surface area covered by reattached flow and decrease due to fewer roughness particles on the solid obstacle surface. Decreasing the porosity and increasing the Reynolds number amplify the effect of the surface roughness on the microscale flow. The results suggest that heat transfer in porous media can be enhanced, if the increase in drag can be overcome. The results also show that the fine roughness regime, which is frequently encountered due to corrosion, is detrimental to the heat transfer performance of porous media.