RANS COMPUTATIONS OF MILD CURVED OPEN CHANNEL FLOWS FOCUSING ON AN OUTER-BANK CELL
RANS COMPUTATIONS OF MILD CURVED OPEN CHANNEL FLOWS FOCUSING ON AN OUTER-BANK CELL
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重点关注外岸单元的温和弯曲明渠流动的RANS计算
DOI：
10.2208/prohe.52.1009
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
W. Balen
中科院分区：
文献类型：
--
作者：
I. Kimura;W. Uijttewaal;T. Hosoda;W. Balen
弯曲明渠水流的特征是横断面二次流的形成。截面流的主要结构分为第一类二次流，它是由离心力引起的。外壁单元在表面和外壁之间的角落附近产生。虽然外滩槽的规模比主二次电流小得多，但外滩槽对外滩的侵蚀有影响。以往的研究表明，外滩胞体是由两种组合效应引发的，即湍流和各向同性和离心力。因此，外岸单元的判据比较复杂。在本研究中，线性和非线性k-E模型应用于Booij（2003）实验研究的轻度弯曲明渠流动。只有非线性模型才能很好地捕捉到外滩单元，并能很好地再现速度和雷诺应力剖面。三阶非线性模型略微提高了精度。不同曲率半径下的计算表明，线性k-E模型也能在非常剧烈的弯曲情况下产生外滩单元。外滩细胞产生的标准模型R/H阈值为22。涡流粘度较低的模型可以在较大R/H的流动中产生外滩胞体。
A curved open channel flow is characterized by formations of cross-sectional secondary currents. The main structure of the cross-sectional flow is classified into the secondary current of 1st kind, which is caused by the centrifugal force. The outer-bank cell is generated near the corner between the surface and the outer-bank. Though the scale of the outer-bank cell is much smaller than the main secondary current, the outer-bank cell affects the erosion of the outer-bank. The previous studies showed that the outer-bank cell is initiated by two combinational effects, i. e., turbulence an-isotropy and the centrifugal force. Therefore, the criterion of the outer-bank cell is rather complicated. In this study, linear and non-linear k-E models are applied to the mild curved open channel flows studied experimentally by Booij (2003) . Only non-linear models could capture the outer-bank cell and could reproduce velocity and Reynolds stress profiles well. A 3rd order non-linear model slightly improved the accuracy. The computations with different curvature radiuses indicate that the linear k-E models can also generate the outer-bank cell in cases of very sharp bend. The threshold of R/H by the standard model for generation of the outer-bank cell was 22. The model with lower eddy viscosity could yield the outer-bank cell in the flows with larger R/H.