發(fā)布時(shí)間：2018-06-04 03:40

  本文選題：水沙兩相流模型 + Eulerian-Lagrangian模型��； 參考：《清華大學(xué)》2016年博士論文

【摘要】：兩相流模型能夠較為準(zhǔn)確地描述水沙兩相間的相互作用,揭示水沙運(yùn)動(dòng)機(jī)理。構(gòu)建高精度、適用性強(qiáng)的水沙兩相流模型對(duì)于完善泥沙運(yùn)動(dòng)理論、解決工程泥沙問(wèn)題有重要的意義。本文旨在完善和發(fā)展水沙兩相流數(shù)學(xué)模型,基于Eulerian-Lagrangian觀點(diǎn)構(gòu)建了一個(gè)適用于懸移質(zhì)泥沙運(yùn)動(dòng)的顆粒軌道模型;基于Eulerian-Eulerian觀點(diǎn)構(gòu)建了一個(gè)可用于大渦模擬的雙流體模型,并引入光滑粒子流體動(dòng)力學(xué)(SPH)方法進(jìn)行求解。論文構(gòu)建的Eulerian-Lagrangian兩相流模型采用包含泥沙體積濃度的雷諾時(shí)均控制方程與k-ε紊流模型描述水相運(yùn)動(dòng)。視泥沙為分散介質(zhì),將泥沙顆粒的運(yùn)動(dòng)速度分解為時(shí)均流速與脈動(dòng)速度,采用運(yùn)動(dòng)方程計(jì)算顆粒時(shí)均流速的變化,耦合渦相干模型(EIM)描述泥沙顆粒在紊動(dòng)水體作用下的脈動(dòng)�？紤]尾流對(duì)顆粒紊動(dòng)的增強(qiáng)效應(yīng)修正渦相干模型以提高模型模擬懸移質(zhì)泥沙紊動(dòng)擴(kuò)散的精度�；诘秃碀舛燃僭O(shè),簡(jiǎn)化兩相控制方程,得到適用于低含沙水流懸移質(zhì)輸沙問(wèn)題的Eulerian-Lagrangian兩相流模型。將模型應(yīng)用于二維明渠恒定均勻流懸移質(zhì)輸沙,計(jì)算了不同的泥沙粒徑條件下懸移質(zhì)相對(duì)濃度垂向分布,討論了粒徑對(duì)泥沙擴(kuò)散系數(shù)的影響。結(jié)果顯示,考慮尾流對(duì)顆粒紊動(dòng)增強(qiáng)效應(yīng)的Eulerian-Lagrangian模型能夠準(zhǔn)確模擬較寬粒徑范圍內(nèi)的懸移質(zhì)泥沙的紊動(dòng)擴(kuò)散。論文構(gòu)建的基于SPH方法的雙流體模型對(duì)連續(xù)介質(zhì)假設(shè)下推導(dǎo)的體積平均控制方程組進(jìn)行空間濾波,采用質(zhì)量濃度加權(quán)的Favre平均得到空間平均的兩相控制方程,采用Smagorinsky公式計(jì)算亞粒子應(yīng)力�？紤]兩相相間作用力、泥沙顆粒粒間作用力以及泥沙對(duì)水相亞粒子應(yīng)力的影響,模型能夠較全面地反映水沙兩相的相互作用。將含沙水流離散成一組SPH粒子,粒子以水相速度運(yùn)動(dòng)并攜帶兩相物理信息。將兩相控制方程改寫為粒子的運(yùn)動(dòng)方程及其攜帶的物理量控制方程,并采用SPH方法離散求解。將雙流體模型應(yīng)用于靜水中拋泥問(wèn)題,討論泥沙云團(tuán)的寬度、下沉速度及濃度分布隨泥沙粒徑與云團(tuán)初始體積的變化規(guī)律。結(jié)果顯示,本文構(gòu)建的雙流體模型能夠準(zhǔn)確描述泥沙云團(tuán)的運(yùn)動(dòng)特性,適用于水沙兩相流問(wèn)題的研究。
[Abstract]:The two-phase flow model can accurately describe the interaction between two phases of water and sediment and reveal the mechanism of water and sediment movement. It is of great significance to construct a high precision and applicable water and sediment two-phase flow model for perfecting the theory of sediment movement and solving the problem of engineering sediment. The purpose of this paper is to perfect and develop the mathematical model of water-sediment two-phase flow, to construct a particle track model suitable for suspended sediment movement based on Eulerian-Lagrangian 's viewpoint, and to construct a two-fluid model which can be used in large eddy simulation based on Eulerian-Eulerian 's viewpoint. The smooth particle hydrodynamics (SPH) method is introduced to solve the problem. The Eulerian-Lagrangian two-phase flow model constructed in this paper uses Reynolds time average control equation including sediment volume concentration and k- 蔚 turbulence model to describe the water phase motion. Considering sediment as a dispersed medium, the motion velocity of sediment particles is decomposed into mean velocity and pulsating velocity, and the variation of average velocity when particles are calculated by the equation of motion. The coupled vortex coherent model (EIMM) is used to describe the pulsation of sediment particles under the action of turbulent water body. Considering the enhancement effect of wake on particle turbulence, the vortex-coherent model is modified to improve the accuracy of simulating the turbulent diffusion of suspended sediment. Based on the assumption of low sediment concentration, the two-phase governing equation is simplified and a Eulerian-Lagrangian two-phase flow model is developed for suspended sediment transport in low-sediment flow. The model is applied to the suspended sediment transport in a two-dimensional open channel with constant uniform flow. The vertical distribution of suspended sediment relative concentration under different sediment particle size is calculated and the influence of particle size on sediment diffusion coefficient is discussed. The results show that the Eulerian-Lagrangian model can accurately simulate the turbulent diffusion of suspended sediment in a wide particle size range. The two-fluid model based on SPH method is used to filter the volumetric average governing equations derived from the continuum medium hypothesis. The two-phase governing equations of the spatial average are obtained by using the mass-concentration weighted Favre average. The subparticle stress was calculated by Smagorinsky formula. Considering the interaction force between two phases, the interaction between sediment particles and the effect of sediment on the stress of subparticle in water phase, the model can fully reflect the interaction between water and sediment. The sediment flow is separated into a group of SPH particles, which move at the velocity of water phase and carry two phase physical information. The two-phase control equation is changed into the motion equation of particles and the governing equation of physical quantities carried by them. The SPH method is used to discretize the solution. The two-fluid model is applied to the slimming problem in hydrostatic water. The variation of sediment cloud width, subsidence velocity and concentration distribution with sediment particle size and cloud initial volume is discussed. The results show that the two-fluid model constructed in this paper can accurately describe the motion characteristics of sediment cloud and is suitable for the study of water-sediment two-phase flow.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：O359

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