Direct Numerical Simulation of the Neutrally Stratified Turbulent Ekman Boundary Layer
Direct Numerical Simulation of the Neutrally Stratified Turbulent Ekman Boundary Layer
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中性分层湍流埃克曼边界层的直接数值模拟
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
H. Kawamura
中科院分区：
文献类型：
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作者：
Katsuhiro Miyashita;K. Iwamoto;H. Kawamura
对光滑表面上的湍流埃克曼边界层进行直接数值模拟 (DNS)。雷诺数 Re f 设置为 Ref = 400、510、600、775、1140 和 1393，其中 Ref 基于地转风 G、运动粘度 ν 和科里奥利参数 f。 Ref=1140和1393的模拟已在地球模拟器上进行。在雷诺数较高的情况下，平均速度剖面与 Caldwell 等人的实验数据表现出良好的一致性。 (1972) 和 Coleman (1999) 的 DNS 数据。在上部区域发现了低速大型结构，而众所周知的条纹结构出现在墙附近。这种大规模结构是在材料线的运动中观察到的。该结构的倾斜度与平均流速的方向不一致。其原因是基于初始位置在墙壁附近水平的材料线的运动来讨论的。此外，还针对所获得的 DNS 数据库检验了 Blackadar (1962, 1965) 提出的涡粘模型。改进后的模型与现有 DNS 的结果非常吻合。
Direct numerical simulations (DNSs) are performed for the turbulent Ekman boundary layer over a smooth surface. The Reynolds numbers Re f are set to be Ref = 400, 510, 600, 775, 1140 and 1393 where Ref is based on the geostrophic wind G, the kinematic viscosity ν and Coriolis parameter f. The simulations of Ref = 1140 and 1393 have been carried out on the Earth Simulator. In the cases of the higher Reynolds numbers, the mean velocity profiles show good agreement with the experimental data of Caldwell et al. (1972) and the DNS data of Coleman (1999). A low-speed large-scale structure is found in the upper region, whereas the well-known streaky structure appears in the vicinity of the wall. This large-scale structure is observed in a motion of a material line. The inclination of this structure does not coincide with the direction of the mean flow velocity. The reason is discussed based upon the motion of a material line whose initial position is horizontal in a vicinity of the wall. In addition, the eddy-viscosity model proposed by Blackadar (1962, 1965) is examined with respect to the obtained DNS data base. The improved model gives good agreement with the results by the present DNS.