A systematic study of turbulent heat transfer over rough walls
A systematic study of turbulent heat transfer over rough walls
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DOI：
10.1016/j.ijheatmasstransfer.2018.08.013
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发表时间：
2018-06
影响因子：
5.2
通讯作者：
P. Forooghi;M. Stripf;B. Frohnapfel
中科院分区：
文献类型：
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作者：
P. Forooghi;M. Stripf;B. Frohnapfel
直接数值模拟用于解决通道中各种粗糙壁上的湍流和传热问题。墙壁的几何形状在模拟中得到了精确解析。目的是了解粗糙度形态及其缩放对相对于表面摩擦的传热增强的影响。检查通过扫描燃气轮机叶片和内燃机获得的许多真实的粗糙表面图以及几个人工生成的粗糙表面。本文的第一部分系统地研究了在恒定粗糙度高度下统计表面特性（即表面坡度和粗糙度密度）的影响，结果表明，雷诺类比因子（两倍斯坦顿数除以表面摩擦系数）随表面参数的变化有意义但适度，但在坡度或密度极低的情况下，雷诺类比因子显着增长并趋于光滑壁。在本文的第二部分中，粗糙度高度发生变化（内部和外部单元独立），同时保持几何相似性。考虑到所有模拟情况，可以得出结论，雷诺类比因子与以内部单位缩放的等效砂粗糙度相关性相当好，并且渐近趋于稳定。
Direct Numerical Simulations are used to solve turbulent flow and heat transfer over a variety of rough walls in a channel. The wall geometries are exactly resolved in the simulations. The aim is to understand the effect of roughness morphology and its scaling on the augmentation of heat transfer relative to that of skin friction. A number of realistic rough surface maps obtained from the scanning of gas turbine blades and internal combustion engines as well as several artificially generated rough surfaces are examined. In the first part of the paper, effects of statistical surface properties, namely surface slope and roughness density, at constant roughness height are systematically investigated, and it is shown that Reynolds analogy factor (two times Stanton number divided by skin friction coefficient) varies meaningfully but moderately with the surface parameters except for the case with extremely low slope or density where the Reynolds analogy factor grows significantly and tends to that of a smooth wall. In the second part of the paper, the roughness height is varied (independently in both inner and outer units) while the geometrical similarity is maintained. Considering all the simulated cases, it is concluded that Reynolds analogy factor correlates fairly well with the equivalent sand roughness scaled in inner units and asymptotically tends to a plateau.