格子Boltzmann方法在含植被河道水流数值模拟中的应用研究

发布时间：2018-05-16 18:45

本文选题：格子Boltzmann方法 + MRT-LBE　；参考：《北方民族大学》2017年硕士论文

【摘要】：天然河道、水库、湖泊中水生植被的存在,干扰了水流流场,从而对泥沙运移、河道演变、水库淤积、水环境和水生态产生较大影响.本文利用三维激光多普勒测速仪(laser Doppler velometer,LDV)等仪器对实验室水槽中含有不同排列方式的植被水流特性进行了实测与分析,并建立了多松弛格子Boltzmann方程(multi-relax time lattice Boltzmann equation,MRT-LBE),研究了其数值算法,并对含植被实验室水槽水流问题进行了数值模拟研究.研究结果具有一定的理论意义和实际工程应用价值,可为河道治理及水生态环境建设提供参考.具体内容包括以下几个方面:首先,综述计算流体动力学的产生、发展历程和与传统数值模拟方法的对比.同时追溯格子Boltzmann方法(lattice Boltzmann Method,LBM)的由来、发展.系统地给出格子Boltzmann方法的离散速度模型、边界处理方式,并利用经典算例进行了验证.其次,利用LDV对实验室水槽中含不同直径、不同排列方式的四种典型工况(稀疏交错、稠密交错、稀疏并排、稠密并排)在非淹没刚性植被的水流结构进行了实测.对实测数据利用Matlab等有关软件进行处理,分析了水流经过植被群前后,水面雍高、流速变化、水面坡降、水力坡降等情况.通过比较分析,得到了四种典型工况下植被区的水流特性.最后,基于LBM对具有刚性植被的实验室水槽水流进行了二维数值模拟研究.由于单松弛模型(SRT)在雷诺数较大时,会出现不稳定现象,本文利用多松弛模型(MRT-LBE)进行数值模拟.根据实测结果与数值模拟结果的对比,在模型中加入了植被“拖曳力”,建立了适用于含植被水流数值模拟的MRT-LBE模型,并给出了具体算法.对四种典型工况下水流运动进行了数值模拟,并与实测结果进行了比较.模拟结果与实测数据相对吻合,表明所建立模型可用于明渠和河流中含植被水流运动.计算机数值模拟时,由于模拟区域的对称性,只对其中一半区域进行模拟,水槽中心线处采用对称性边界条件进行处理.这样不仅可节约计算量,也可以节约计算机内存.对于固壁采用反弹边界条件进行处理,进口边界根据实测数据给出,出口边界为充分发展边界。
[Abstract]:The existence of aquatic vegetation in natural rivers, reservoirs and lakes interferes with the flow field, which has a great influence on sediment transport, river evolution, reservoir deposition, water environment and water ecology. This paper uses laser Doppler velometer (LDV) and other instruments for different arrangement of vegetation water in the laboratory water tank. The flow characteristics are measured and analyzed, and the multi relaxation lattice Boltzmann equation (multi-relax time lattice Boltzmann equation, MRT-LBE) is established, and its numerical algorithm is studied. The numerical simulation of the water flow problem in the water tank with vegetation laboratory is studied. The results have some theoretical significance and practical engineering application value. It provides reference for river management and water ecological environment construction. The specific contents include the following aspects: first, it summarizes the generation of computational fluid dynamics, the development process and the comparison with the traditional numerical simulation methods. At the same time, the origin of the lattice Boltzmann method (lattice Boltzmann Method, LBM) is traced, and the lattice Boltzmann method is systematically given. The discrete velocity model, the boundary treatment method and the classic example are verified. Secondly, the flow structure of the non submerged rigid vegetation is measured by four typical working conditions (sparse staggered, dense staggered, sparse side by side, dense side by side) in the laboratory water tank with different diameters and different arrangement modes in the laboratory water tank with LDV. Matlab and other related software are processed, and the water flow passes through the vegetation group, the water surface Yonggao, the flow velocity change, the water surface slope, the hydraulic slope and so on. Through the comparative analysis, the flow characteristics of the vegetation area under the four typical conditions are obtained. Finally, the two-dimensional numerical simulation of the water flow in the laboratory water tank with rigid vegetation is carried out based on the LBM. In this paper, the single relaxation model (SRT) will be unstable when the Reynolds number is large. In this paper, the multi relaxation model (MRT-LBE) is used to simulate the numerical simulation. According to the comparison between the measured results and the numerical simulation results, the "towing force" of the vegetation is added to the model, and a MRT-LBE model suitable for the numerical simulation of the vegetation flow is set up, and the results are given. The numerical simulation of flow motion under four typical operating conditions is carried out and compared with the measured results. The simulation results are in good agreement with the measured data, which shows that the established model can be used for the movement of the vegetation flow in the open channel and the river. In the simulation, the center line of the sink is treated with symmetric boundary conditions. This can not only save calculation and save computer memory, but also deal with the bounce boundary condition for the solid wall, and the import boundary is given according to the measured data, and the exit boundary is fully developed boundary.

【学位授予单位】：北方民族大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O35

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