细颗粒泥沙净冲刷和输移的大涡模拟研究

发布时间：2018-08-02 15:41

【摘要】：在传统水沙输移数值模拟研究中一般采用雷诺时均模拟技术(Reynolds-averaged simulation,RANS).与RANS相比,大涡模拟技术(large eddy simulation,LES)能够更加精确反映细部流动结构,计算机的发展使得采用LES探讨水流和泥沙运动规律成为可能.本文尝试给出净冲刷条件下悬沙计算的边界条件,采用动态亚格子模式对循环槽道和长槽道中的水流运动和泥沙输移进行了三维大涡模拟研究.利用直接数值模拟(direct numerical simulation,DNS)结果对LES模型进行了率定,计算结果符合良好,在此基础上初步探讨了泥沙浓度、湍动强度和湍动通量等的分布特征.结果表明,净冲刷条件下输沙平衡时泥沙浓度符合Rouse公式分布,单向流动中泥沙浓度沿着流向逐渐增大.泥沙浓度湍动强度和湍动通量都在近底部达到最大值,沿着垂向迅速减小.湍动黏性系数和扩散系数基本上在水深中间处达到最大.湍动Schmidt数沿着水深方向不是常数,在近底部和自由水面附近较大,在水深中间处较小.
[Abstract]:In the traditional numerical simulation of water and sediment transport, the Reynolds time averaged simulation (Rans) technique is generally used. Compared with RANS, the large eddy simulation (large eddy simulation les) can more accurately reflect the detailed flow structure. With the development of computer, it is possible to use LES to study the law of water flow and sediment movement. In this paper, the boundary conditions for the calculation of suspended sediment under the condition of net scour are attempted, and the three-dimensional large eddy simulation of the flow and sediment transport in the circulation channel and the long channel is carried out by using the dynamic sub-lattice model. The results of direct numerical simulation of (direct numerical are used to determine the rate of LES model, and the calculated results are in good agreement. On this basis, the distribution characteristics of sediment concentration, turbulent intensity and turbulent flux are preliminarily discussed. The results show that the sediment concentration under the condition of net scour is consistent with the distribution of Rouse formula, and the concentration of sediment increases gradually along the flow direction in the unidirectional flow. The turbulent intensity and flux of sediment concentration reach the maximum near the bottom and decrease rapidly along the vertical direction. The turbulent viscosity coefficient and diffusion coefficient basically reach the maximum at the middle of the water depth. The turbulent Schmidt number is not constant along the direction of water depth and is larger near the near bottom and near the free water surface and smaller in the middle of the water depth.
【作者单位】：中国灌溉排水发展中心;清华大学水利水电工程系水沙科学与水利水电工程国家重点实验室;北京中灌绿源国际咨询有限公司;
【分类号】：TV149

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