应用大涡数值计算模拟水下重力流的初步研究

发布时间：2018-02-02 22:51

本文关键词： 大涡模拟重力流湍动能谱拟序结构　出处：《安徽工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：大涡模拟是一种重要的湍流模拟方法，其结果中包含了湍流中的长度尺度大于滤波宽度的脉动运动，它能够得到比雷诺平均方程方法更多的湍流信息，又比直接数据模拟方法所需要的计算资源少得多。本文采用大涡模拟对前人所做的闸门释放重力流实验进行了模拟，对比了二维与三维大涡模拟以及雷诺平均模拟的差别，并采用涡耗散模型对二维重力流大涡模拟进行了模型改良，分析了重力流的湍动能谱和湍流拟序结构，，讨论了非均匀网格和亚格子模型对重力流大涡模拟产生的影响，得出一些结论如下：（1）三维大涡模拟比二维大涡模拟能够更好地反映出重力流中的大尺度运动，其湍动能谱中存在满足－5/3幂次律的惯性子区；（2）大涡模拟能够再现重力流中两种不同湍流机制，非粘性自由剪切及粘性壁面湍流机制主导的区域内的湍流拟序结构，包括Kelvin-Helmholtz滚动、条带状结构和横向涡拟序结构；（3）三维大涡模拟与三维雷诺平均方法的湍能谱在雷诺平均尺度范围内重合，在脉动尺度范围内两者出现了分离，并且在雷诺平均方法的湍能谱中没有观察到实验和理论都已经证明了的－5/3幂次律。（4）膨胀系数为恒定1.03以下非均匀网格带来的交换误差对三维大涡模拟结果产生的影响比较小，说明我们所采用的三维大涡模拟可以在非均匀网格上进行；（5）比较了动力Smagorinsky模型、标准Smagorinsky模型以Liu-Meneveau-Katz尺度相似模型，结果显示动力Smagorinsky模型模拟效果最好，Liu-Meneveau-Katz尺度相似模型最差；但是Liu-Meneveau-Katz尺度相似模型与标准Smagorinsky模型的混合模型的模拟效果与动力Smagorinsky模型相近，且所需要的计算代价小于动力Smagorinsky模型。上述研究成果对于后续的在复杂地形上含有沉积物的重力流研究中应用大涡模拟有一定的参考作用。
[Abstract]:Large eddy simulation is an important turbulence simulation method, whose results include the pulsating motion of the length scale larger than the filter width in the turbulence, which can obtain more turbulence information than the Reynolds average equation method. In this paper, a large eddy simulation is used to simulate the gravity flow from the gate. The differences between 2D and 3D large vortices simulation and Reynolds average simulation are compared, and the vortex-dissipation model is used to improve the two-dimensional gravity flow simulation. The turbulent kinetic energy spectrum and turbulent sequence structure of gravity flow are analyzed. The influence of non-uniform grid and sub-lattice model on the large eddy simulation of gravity flow is discussed. Some conclusions are as follows: (1) Three-dimensional large eddy simulation can better reflect the large-scale motion in gravity flow than two-dimensional large eddy simulation, and there is an inertial sub-region in the turbulent kinetic energy spectrum which satisfies the -5 / 3 power law. 2) large eddy simulation can reproduce the turbulent quasi-sequence structure in the region dominated by non-viscous free shear and viscous wall turbulence. It includes Kelvin-Helmholtz rolling, strip structure and transverse vortex structure. 3) the turbulent spectra of 3-D large eddy simulation and 3-D Reynolds mean method coincide in the range of Reynolds mean scale, and they are separated in the range of pulsating scale. And in the turbulent energy spectrum of the Reynolds mean method, the law of -5 / 3 power law, which has been proved by both experiment and theory, has not been observed. The exchange error caused by the inhomogeneous mesh with a constant expansion coefficient below 1.03 has little effect on the results of 3D large eddy simulation. The results show that the 3D large eddy simulation can be carried out on a non-uniform grid. The dynamic Smagorinsky model and the standard Smagorinsky model are compared with the Liu-Meneveau-Katz scale similarity model. The results show that the dynamic Smagorinsky model is the best and the Liu-Meneveau-Katz scale model is the worst. However, the simulation effect of the mixed model of Liu-Meneveau-Katz scale similarity model and standard Smagorinsky model is similar to that of dynamic Smagorinsky model. The computational cost required is less than that of the dynamic Smagorinsky model. The results mentioned above can be used as a reference for the subsequent study of gravity flow with sediment on complex terrain using large eddy simulation. .
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV135

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