本文選題：計算流體力學　切入點：自由面運動　出處：《浙江大學》2016年碩士論文　論文類型：學位論文

【摘要】：自由面運動是自然界中的一種常見現(xiàn)象,與人類的生存發(fā)展息息相關,在科學研究和工程應用中都有著重要的價值.然而,自由面運動是一種復雜的現(xiàn)象,尤其是強非線性自由面的運動,目前仍然存在很多難題有待解決.近些年來,CFD (Computational Fluid Dynamics,計算流體力學)已經(jīng)被證明是一種研究自由面運動的有效手段并被廣泛應用到相關研究中.本文采用自主發(fā)展的CIP-ZJU (Constraint Interpolation Profile Model in Zhejiang Univer-sity)模型來研究強非線性自由面運動,流場求解器方面,本模型采用時間,空間均為三階的CIP方法保證了對流項的高精度求解；采用中心差分格式進行擴散性的求解；采用超松弛迭代方法求解壓力Poisson方程.自由面捕捉方面,本模型包括兩種高精度的VOF (Volume of Fluid,流體體積法)和一種質(zhì)量守恒型的Level Set方法.同時,本文引入了基于密度重構(gòu)的平衡型CSF (Continuum Surface Force)模型以及針對于歐拉網(wǎng)格下同種液體不同相之間界面追蹤的雙液相VOF方法.根據(jù)建立的模型,開展了強非線性自由面運動問題的數(shù)值模擬,包括潰壩問題,液滴沖擊自由面,氣泡上升,水面結(jié)構(gòu)物附近波浪誘導渦等.在潰壩問題的數(shù)值研究中,本文首先根據(jù)實驗結(jié)果得到一個潰壩試驗中擋板運動的經(jīng)驗公式并進行驗證,并應用于干底床和濕底床潰壩問題潰壩的數(shù)值研究,重點分析了擋板運動對于潰壩問題中水舌運動,自由面形態(tài),壓力變化等影響；此外還開展了液滴沖擊自由面和三維氣泡上升的數(shù)值模擬,重點觀測了其演變過程中表面張力的作用及自由面的運動;在水面結(jié)構(gòu)物附近波浪誘導渦的初步數(shù)值研究中,本文對規(guī)則波作用下不同寬度,縱深的薄板附近波浪誘導渦進行了數(shù)值觀測,對于水面結(jié)構(gòu)物附近誘導渦的運動規(guī)律有了初步的認識,為未來更深入的研究打下了良好的基礎.本文的主要創(chuàng)新點如下：(1)提出了一種雙液相VOF方法,實現(xiàn)了歐拉坐標系下同種流體不同相多相流體之間追蹤和相互作用研究,并成功將其應用到濕底床潰壩的數(shù)值研究中.(2)提出了一種質(zhì)量守恒型的Level Set方法,有效改進了Level Set方法的質(zhì)量守恒率.(3)根據(jù)實驗公式給出了一個潰壩試驗中擋板運動的經(jīng)驗公式并將公式應用到數(shù)值模型中,改進了潰壩數(shù)值模擬的精度.(4)系統(tǒng)地研究了潰壩問題中擋板運動對潰壩水舌傳播,自由面演變,后方直墻沖擊壓力的影響.
[Abstract]:Free surface motion is a common phenomenon in nature, closely related to the survival and development of human beings, and has important value in scientific research and engineering applications. However, free surface motion is a complex phenomenon. Especially the motion of strongly nonlinear free surface, There are still many problems to be solved. In recent years, Computational Fluid Dynamics (CFD) has been proved to be an effective method to study free surface motion and has been widely used in related research. The CIP-ZJU constraint Interpolation Profile Model in Zhejiang Univer-sitymodel is used to study strongly nonlinear free surface motion. In the aspect of flow field solver, the CIP method of time and space is adopted to ensure the accurate solution of the convection term, and the central difference scheme is used to solve the diffusivity. The overrelaxation iterative method is used to solve the pressure Poisson equation. In the aspect of free surface capture, this model includes two kinds of high-precision VOF volume of fluid (fluid volume method) and a mass-conserved Level Set method. In this paper, the equilibrium CSF continuous Surface Force model based on density reconstruction and the two-phase VOF method for the interface tracing between different phases of the same liquid under Eulerian grid are introduced. Numerical simulation of strongly nonlinear free surface motion is carried out, including dam-break problem, droplet impact on free surface, bubble rise, wave induced vorticity near water surface structure, and so on. Based on the experimental results, an empirical formula of baffle motion in dam-break test is obtained and verified in this paper, and it is applied to the numerical study of dam-break in dry bed and wet bed. The effects of baffle motion on the motion of water tongue, free surface and pressure are analyzed, and the numerical simulation of droplet impact on free surface and three dimensional bubble rise is also carried out. The effect of surface tension and the motion of free surface are observed in detail. In the preliminary numerical study of wave-induced vortices near water surface structures, different widths of regular waves are studied in this paper. The wave-induced vortex near the thin plate in depth is observed numerically, and the motion law of the induced vortex near the water surface structure is preliminarily understood. The main innovation of this paper is as follows: 1) A two-phase VOF method is proposed to study the tracing and interaction between different phases of the same fluid in Eulerian coordinate system. A mass conserved Level Set method is proposed, which is successfully applied to the numerical study of dam-break in wet bed. The mass conservation rate of Level Set method is improved effectively. (3) based on the experimental formula, an empirical formula of baffle motion in dam break test is given and applied to the numerical model. In this paper, the influence of baffle motion on the propagation of dam-break water tongue, the evolution of free surface and the impact pressure of rear straight wall are studied systematically.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TV122.4

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