【作者】 徐卫东；

【导师】 李治勤；

【作者基本信息】 太原理工大学 ， 水力学及河流动力学， 2011， 硕士

【摘要】 计算流体力动力学(简称CFD)是建立在经典流体力学与数值计算方法基础之上的一门新型独立学科,通过计算机数值计算和图像显示的方法,在时间和空间上定量描述流场的数值解,从而达到对物理问题研究的目的,它客服了理论分析方法对于大量非线性情况不能给出解析结果和试验方法受到测量精度、经费投入、人力和物力的巨大耗费及周期长的缺点。它兼有理论性和实践性的双重特点,成功应用于水利、航运、海洋、环境等流体工程领域。河道糙率在洪水演进计算、河道整治规划等水力计算中常常用到,其主要用于推求河道水面线。河道糙率对水面线的灵敏度非常大,其准确程度对计算精度有很大影响。在洪水演进计算中,河道糙率与设计洪水位的计算密切相关；在河道整治规划中河道糙率影响到土石方开挖和回填的计算,只有选取了合适的河道糙率才能确定出合理、经济的工程规模。本文利用CFD软件Fluent,采用水气两相流的VOF方法与标准k-ε紊流模型相耦合,对具有群潜坝的河道水流流场进行了数值模拟,旨在探求群潜坝对河道糙率影响的机理,以求对物理模型试验的结果进行进一步完善。本文研究内容为校自选项目“群潜坝对河道糙率影响试验研究”的后续研究内容；通过对坝间距为50cm、25cm、12.5cm、6.25cm与原河道(没有布置潜坝),流量分别为4m3/h.8m3/h、15m3/h、25m3/h、45m3/h、75m3/h共30种工况下河道水流流场的数值模拟,分析了建有群潜坝的河道其糙率的变化,得到了坝间距、水深坝高比对河道糙率的影响规律,并进一步分析了群潜坝对河道糙率影响的机理。所得结论如下：1)FLUENT软件用于计算建有群潜坝的河道水流流场是可行的；2)河道中布置群潜坝后,水流流速分布与原河道(没有布置群潜坝的河道)中水流流速分布相似；3)河道通过某一流量时,对同一河道断面而言,河道糙率随着坝间距的减小而增大；4)在群潜坝布置段,水深坝高比的变化对对河道糙率影响较大；群潜坝布置段下游,水深坝高比对河道糙率影响较小；5)群潜坝对其布置段下游河道的糙率基本没有影响,群潜坝布置段下游河道糙率与原河道糙率基本相等；6)在坝间距一定的情况下,对同一河道断面而言,河道糙率随着水深坝高比的增大而减小；7)相同坝间距和水深坝高比情况下,河道糙率沿程减小。即群潜坝对河道糙率的影响是沿程减小的；当水深坝高比增大到一定程度后,河道糙率趋于稳定,不再沿程发生变化；8)河道通过某一流量时,随着坝间距的减小(即潜坝数量增多),河道内水流流速从上游到下游变大的幅度增大；9)潜坝迎水面流速矢量分散,流速较小,潜坝背水面流速矢量集中,流速较大；潜坝背水面出现漩涡(即负压区)。10)潜坝迎水面流速等值线条数较少,覆盖范围较大,流速较小；潜坝背水面流速等值线条数较多,而且覆盖范围小,比较集中,流速较大。更多还原

【Abstract】 Computational Fluid Dynamics (short title CFD) is a new independent subject that is based on the classical hydromechanics and numerical calculation method. Through the method of computer numerical calculation and image display, it describes the flow field numerical solution quantitatively in time and space, so as to achieve the goal of the research of physical problems. It overcomes the weakness that the theoretical analysis method cannot give the analytical results for most nonlinear situation and the test methods are affected by measuring precision, funds, manpower and material resources of the huge cost and long circle. It has the double characteristics of theory and practice, and is applied in water conservancy,shipping,Marine,environment and other fluid engineering field successfully.River channel roughness often is used in hydraulic calculation such as floods evolution calculation, river channel regulation and so on. It is mainly used to inquire the water surface line. River channel roughness is very sensitivity to water surface line.Its precision has a great influence on calculation accuracy. In the floods evolution calculation, river channel roughness is closely related to the calculation of design flood level; in river channel regulation,river channel roughness affects the excavation and backfilling calculation in cubic meter of earth and stone. Only select appropriate river channel roughness can formulate reasonable, economical project scale.This text using CFD software Fluent, coupling VOF method of two phase flow and k-εturbulence model, making the numerical simulation for river flow field with the submerged dikes, is aimed at exploring the submerged dikes’ influencing mechanism to river channel roughness, in order to make the result of physical model test further perfection.This paper studies the content for the project which selectes from follow-up research of the school project "the experimental study of the submerged dikes’inference on river channel roughness";With regard to those flow fields of river channels with 50cm、25cm、12.5cm、6.25cm spacing’dikes and original river channel corresponding to flow 4m3/h、8m3/h、15m3/h、25m3/h、75m3/h, total of 30 kinds of working conditions, the author conduct numerical simulation research, analyze variation of roughness of river channel of building submerged dikes, receive the influence law of the ratio between the water depth and dike height for roughness of river channel and further analyze the influence mechanism of submerged dikes for river channel roughness.The results are following conclusions:1) FLUENT software used for the calculation of river flow field of river channel of building submerged dikes is basically feasible; 2) After the arrangement of submerged dikes,the water velocity distribution is similar to the velocity distribution of the original river; 3) When a flow pass river channel, river channel roughness will increase,while dikes’spacing reduce for the same water cross section; 4) In submerged dikes’sections, river channel roughness is largely influenced by variation of the ratio between the water depth and dike height; the downstream of submerged dikes’sections, river channel roughness is little influenced.5) The inference on river channel roughness for the downstream of submerged dikes’sections can be ignored, the roughness of submerged dikes’ downstream is equals to the roughness of the original channel; 6) when the dikes’spacing is unchanged, river channel roughness will reduce when the ratio between the water depth and dike height increased,for the same water cross section; 7) For the same dikes’spacing and the ratio between the water depth and dike height, river channel roughness will reduce along the river channel; The submerged dikes’inference on river channel roughness is reduced along the river channel; when the ratio between the depth and dam height reached to a certain level,the river channel roughness will no longer changed along the river channel; 8) When a flow pass river channel, with the decrease of the dikes’spacing, the Margin of becoming large Of flow velocity from upstream to downstream increases; 9) The velocity vector of water positive side of the submerged dike is scattered and small; the dorsal surface of the submerged dike, the velocity vector is concentrated and great; the dorsal surface of the submerged dike,there is whirlpool(Negative pressure area); 10) The velocity vector equivalent lines of water positive side of the submerged dike is few and covers a large area and the velocity is small; The velocity vector equivalent lines of the dorsal surface of the submerged dike is concentrated and great and covers large area.更多还原