Momentum balance in flows over mobile granular beds: application of double-averaging methodology to DNS data
Momentum balance in flows over mobile granular beds: application of double-averaging methodology to DNS data
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DOI：
10.1080/00221686.2016.1260656
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发表时间：
2017-01
影响因子：
2.3
通讯作者：
B. Vowinckel;V. Nikora;Tobias Kempe;J. Fröhlich
中科院分区：
文献类型：
--
作者：
B. Vowinckel;V. Nikora;Tobias Kempe;J. Fröhlich
摘要：本文介绍了双平均方法在浸没边界法直接数值模拟得到的移动床条件下的实际数据中的应用。计算域的尺寸与相对淹没较小的明渠流相似。畴底是一个平面，上面覆盖着一层固定在床上的六边形排列的单尺寸球体。固定的颗粒被2000个相同大小的可移动颗粒覆盖，这些颗粒可以自由移动。研究了两种截然不同的Shields参数值下完全动员和部分动员颗粒床的模拟情况。首先确定了平均时间、平均区域大小和形状对双平均流量的影响。然后，对移动床条件下的双平均动量平衡方程的关键项进行了详细评价。本文表明，双平均方法可以有效地将完全解析模拟产生的大量数据集减少到可管理的物理上有意义的双平均量，这应该有助于设计模拟移动床流的封闭策略。
ABSTRACT This paper presents the application of the double-averaging methodology to actual data obtained for the mobile-bed conditions from direct numerical simulations using an immersed boundary method. The dimensions of the computational domain resemble those for open-channel flows with small relative submergence. The domain bottom is a plane covered with one layer of hexagonally packed, single-size spheres fixed to the bed. The fixed particles are covered by 2000 mobile particles of the same size that are free to move. Two simulation scenarios at distinctly different values of the Shields parameter are studied representing a fully mobilized and partially mobilized granular bed. The effects of the averaging time and the averaging domain size and shape on the double-averaged flow quantities are identified first. Then, the data analysis focuses on the detailed assessment of the key terms of the double-averaged momentum balance equation formulated for mobile-bed conditions. The paper demonstrates that the double-averaging methodology provides an efficient reduction of the massive datasets produced by the fully resolved simulations to a manageable number of physically meaningful double-averaged quantities, which should help devising closure strategies for modelling mobile-bed flows.