本文選題：格子Boltzmann方法 + MRT-LBE�。� 參考：《北方民族大學(xué)》2017年碩士論文

【摘要】：天然河道、水庫(kù)、湖泊中水生植被的存在,干擾了水流流場(chǎng),從而對(duì)泥沙運(yùn)移、河道演變、水庫(kù)淤積、水環(huán)境和水生態(tài)產(chǎn)生較大影響.本文利用三維激光多普勒測(cè)速儀(laser Doppler velometer,LDV)等儀器對(duì)實(shí)驗(yàn)室水槽中含有不同排列方式的植被水流特性進(jìn)行了實(shí)測(cè)與分析,并建立了多松弛格子Boltzmann方程(multi-relax time lattice Boltzmann equation,MRT-LBE),研究了其數(shù)值算法,并對(duì)含植被實(shí)驗(yàn)室水槽水流問(wèn)題進(jìn)行了數(shù)值模擬研究.研究結(jié)果具有一定的理論意義和實(shí)際工程應(yīng)用價(jià)值,可為河道治理及水生態(tài)環(huán)境建設(shè)提供參考.具體內(nèi)容包括以下幾個(gè)方面:首先,綜述計(jì)算流體動(dòng)力學(xué)的產(chǎn)生、發(fā)展歷程和與傳統(tǒng)數(shù)值模擬方法的對(duì)比.同時(shí)追溯格子Boltzmann方法(lattice Boltzmann Method,LBM)的由來(lái)、發(fā)展.系統(tǒng)地給出格子Boltzmann方法的離散速度模型、邊界處理方式,并利用經(jīng)典算例進(jìn)行了驗(yàn)證.其次,利用LDV對(duì)實(shí)驗(yàn)室水槽中含不同直徑、不同排列方式的四種典型工況(稀疏交錯(cuò)、稠密交錯(cuò)、稀疏并排、稠密并排)在非淹沒(méi)剛性植被的水流結(jié)構(gòu)進(jìn)行了實(shí)測(cè).對(duì)實(shí)測(cè)數(shù)據(jù)利用Matlab等有關(guān)軟件進(jìn)行處理,分析了水流經(jīng)過(guò)植被群前后,水面雍高、流速變化、水面坡降、水力坡降等情況.通過(guò)比較分析,得到了四種典型工況下植被區(qū)的水流特性.最后,基于LBM對(duì)具有剛性植被的實(shí)驗(yàn)室水槽水流進(jìn)行了二維數(shù)值模擬研究.由于單松弛模型(SRT)在雷諾數(shù)較大時(shí),會(huì)出現(xiàn)不穩(wěn)定現(xiàn)象,本文利用多松弛模型(MRT-LBE)進(jìn)行數(shù)值模擬.根據(jù)實(shí)測(cè)結(jié)果與數(shù)值模擬結(jié)果的對(duì)比,在模型中加入了植被“拖曳力”,建立了適用于含植被水流數(shù)值模擬的MRT-LBE模型,并給出了具體算法.對(duì)四種典型工況下水流運(yùn)動(dòng)進(jìn)行了數(shù)值模擬,并與實(shí)測(cè)結(jié)果進(jìn)行了比較.模擬結(jié)果與實(shí)測(cè)數(shù)據(jù)相對(duì)吻合,表明所建立模型可用于明渠和河流中含植被水流運(yùn)動(dòng).計(jì)算機(jī)數(shù)值模擬時(shí),由于模擬區(qū)域的對(duì)稱性,只對(duì)其中一半?yún)^(qū)域進(jìn)行模擬,水槽中心線處采用對(duì)稱性邊界條件進(jìn)行處理.這樣不僅可節(jié)約計(jì)算量,也可以節(jié)約計(jì)算機(jī)內(nèi)存.對(duì)于固壁采用反彈邊界條件進(jìn)行處理,進(jìn)口邊界根據(jù)實(shí)測(cè)數(shù)據(jù)給出,出口邊界為充分發(fā)展邊界。
[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.

【學(xué)位授予單位】：北方民族大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O35

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