共查询到20条相似文献，搜索用时 31 毫秒
1.
建立了二维非恒定渗流的有限元并行计算模型,在windows操作系统下实现了基于消息传递的二维渗流的有限元并行计算。模型采用广义极小残余算法(GMRES)对方程组进行并行迭代求解,通过分析数据执行时的相关性和检验算法结构的固有串行性,将原有串行算法中的算法元直接并行化。对溪洛渡上游围堰的渗流分析进行了并行数值模拟,并针对水位骤降情况下非恒定渗流进行了并行计算,证明了模型的合理性。对模型进行了加速比测定,可以看出并行计算的效率随着问题规模的增加而逐渐提高。 相似文献
2.
Roughness and tortuosity influence groundwater flow through a fracture. Steady flow through a single fracture can be described primitively by the well-known Cubic Law and Reynolds equation with the assumption that the fracture is made of smooth parallel plates. However, ignoring the roughness and tortuosity of the fracture will lead to inaccurate estimations of the flow rate. To obtain a more accurate flow rate through a rough fracture, this paper has derived a modified governing equation, taking into account the three-dimensional effect of the roughness. The equation modifies the Reynolds equation by adding correction coefficients to the terms of the flow rates, which are relative to the roughness angles in both the longitudinal and transverse directions. Experiments of steady seepage flow through sawtooth fractures were conducted. The accuracy of the modified equation has been verified by comparing the experimental data and the theoretical computational data. Furthermore, three-dimensional numerical models were established to simulate the steady flow in rough fractures with the triangular, sinusoidal surfaces and the typical joint roughness coefficient (JRC) profiles. The simulation results were compared with the calculation results of the modified equation and the current equations. The comparison indicates that the flow rate calculated by the modified equation is the closest to the numerical result. 相似文献
3.
岩体裂隙网络非稳定渗流分析与数值模拟 总被引：1，自引：0，他引：1
针对裂隙岩体的非稳定渗流问题,通过将Darcy定理扩展到包含干区的整个裂隙网络区域,并令潜在溢出边界条件为Signorini型互补边界条件,将湿区上的非稳定渗流问题转化为全域上的一个新的初边值问题。为降低试探函数选取的难度,建立与定义在整个裂隙网络区域上的偏微分方程（PDE）提法等价的抛物型变分不等式（PVI）提法,并给出裂隙网络非稳定渗流分析的有限元数值分析格式和迭代算法,与砂槽模型试验数据的对比分析,验证其有效性。最后,将文中发展的计算方法应用到含复杂裂隙网络的边坡非稳定渗流分析,计算结果很好地反映出边坡内部自由面随库水降落的变化规律,并能准确地描述裂隙网络内部渗流运动特征及流量分布的不均匀性。 相似文献
4.
等效水力隙宽和水力梯度对岩体裂隙网络非线性渗流特性的影响 总被引：1，自引：0，他引：1
等效水力隙宽和水力梯度是影响岩体裂隙网络渗流特性的重要因素。制作裂隙网络试验模型,建立高精度渗流试验系统;求解纳维-斯托克斯方程,模拟流体在裂隙网络内的流动状态,研究等效水力隙宽和水力梯度对非线性渗流特性的影响。结果表明,当水力梯度较小时,等效渗透系数保持恒定的常数,流体流动属于达西流动区域,流量与压力具有线性关系,可采用立方定律计算流体流动;当水力梯度较大时,等效渗透系数随着水力梯度的增加而急剧减少,流体流动进入强惯性效应流动区域,流量与压力具有强烈的非线性关系,可采用Forchheimer方程计算流体流动。随着等效水力隙宽的增加,区别线性和非线性流动区域的临界水力梯度呈幂函数关系递减。当水力梯度小于临界水力梯度时,控制方程可选立方定律;当水力梯度大于临界水力梯度时,控制方程可选Forchheimer方程,其参数A和B可根据经验公式计算得到。其研究结果可为临界水力梯度的确定及流体流动控制方程的选取提供借鉴意义。 相似文献
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基于离散裂隙网络模型的裂隙水渗流计算 总被引：1，自引：1，他引：0
离散裂隙网络模型(Discrete Fracture Network（DFN）)是研究裂隙水渗流最为有效的手段之一。文章根据裂隙几何参数和水力参数的统计分布,利用Monte Carlo随机模拟技术生成二维裂隙网络,基于图论无向图的邻接矩阵判断裂隙网络的连通,利用递归算法提取出裂隙网络的主干网或优势流路径。基于立方定律和渗流连续性方程,利用数值解析法建立了二维裂隙网络渗流模型,分析不同边界条件下裂隙网络中的流体流动。结果表明,该方法可以模拟区域宏观水力梯度和边界条件下,裂隙网络水力梯度方向总的流量,以及节点的水位、节点间的流量和流动方向的变化特征,为区域岩溶裂隙水渗流计算提供了一种实用、可行的方法。 相似文献
7.
三相耦合渗流侵蚀管涌机制研究及有限元模拟 总被引：1，自引：0，他引：1
管涌的发生、发展过程是土骨架相在渗流作用下侵蚀为可动细颗粒相,并随水相在孔隙通道中运移流失的过程。在该过程中,渗流与侵蚀相互耦合,相互促进,水相、土相、可动细颗粒相互作用,因此,管涌过程是一个多场、多相耦合的高度非线性的动态过程。现有的管涌试验结果表明,只有当水力梯度大于起始水力梯度时,细颗粒相才会随水相从土体中运移流失,土体才会发生管涌侵蚀,且管涌稳定后土体的孔隙率（稳定孔隙率）和水力梯度之间存在对应关系,根据该结果,提出管涌稳定孔隙率的概念,修正传统的渗流侵蚀本构方程,建立多孔介质中三相耦合的修正的渗流侵蚀管涌控制方程。最后,针对特定应力状态下的土体建立稳定孔隙率和水力梯度之间的对应关系。基于Galerkin有限元法编制有限元程序,在轴对称情况下对该土体的管涌过程进行数值模拟。结果表明,修正后的管涌控制方程能更全面地描述管涌发生、发展直至稳定状态的特性。 相似文献
8.
《Computers and Geotechnics》2006,33(6-7):305-315
A regional seepage field is usually simulated by 2D horizontal seepage finite element method (FEM). However, the Dupuit assumption means that it does not take into account hydraulic head loss caused by vertical flow. In order to simulate a regional seepage field containing suspended cut-off walls by 2D horizontal FEM without any loss of accuracy and efficiency, a zero-thickness element is introduced. The zero-thickness element is used to model suspended cut-off walls and take into account the hydraulic head loss caused by vertical flow near the walls. The matrix equation is deduced. The deduction is based on the resistance coefficient method and the analytical solution of flow near suspended cut-off walls under plane condition. The accuracy of the method is assessed by comparing with 3D FEM results. These coincide with each other both in discharge and hydraulic head. The method is an effective way to simulate a suspended cut-off wall in a regional seepage field with 2D horizontal FEM. 相似文献
9.
基于渗流和管流耦合的管涌数值模拟 总被引：6，自引：0，他引：6
堤坝地基的渗透变形过程实际上是“土中水”转变为“水中土”的过程。在渗透变形发生的集中管涌通道区域,采用常规渗流分析理论,单纯增大管涌通道渗透系数的方法是不太合适的。在未发生渗透变形的区域,用常规渗流理论计算;在管涌通道区域,用管流理论,公共边界上两者之间水头相等、流量大小相等且方向相反,能够较好符合渗透变形的发展规律。为了适应计算过程中内部边界条件不断变化的特点,采用无网格法伽辽金法（element free Galerkin method,EFG）对渗流场进行计算。算例计算表明,这种渗流-管流耦合的方法能够模拟管涌通道绕过防渗墙等复杂的发展过程。 相似文献
10.
考虑气相影响的降雨入渗过程分析研究 总被引：4，自引：1，他引：3
降雨入渗过程是水在下渗的过程中驱替空气的水-气二相流过程,对这一过程的精确模拟一直是渗流计算的难点,目前的处理方法通常是忽略孔隙气压力变化的影响。根据多相流理论,结合质量守恒定律和达西定律,建立了水-气二相流模型,模型的求解采用积分有限差分法和Newton-Raphson迭代方法,通过变换主要变量来表达相态的变化,实现了水相、气相边界条件及降雨入渗边界的精确模拟。利用上述模型对一土柱试验进行模拟,从而验证了模型的正确性,研究了一均质土层的降雨入渗过程,得到了孔隙水压力、孔隙气压力和毛细压力及含水率的变化过程。根据入渗率与地表孔隙气压力的变化关系,验证了孔隙气压力的增大对入渗水流产生阻滞作用。在求解非稳定渗流问题中,考虑空气压力变化的影响是值得研究的。 相似文献
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高渗压小水力梯度岩石渗透性测试 总被引：1，自引：0，他引：1
对低渗透岩石的渗透性测试一般采用瞬时压力脉冲法,但该方法不能真实模拟野外高孔隙水压力、小水力梯度的现场实际条件,而且试验存在较大误差。为此开发研制了一套新型高压渗透仪,在渗透出水端安装了管路过滤器、调速阀两种器械元件,可手动任意调控流量大小,而流量大小采用精确测量渗出水体积变化量表示。试验只要保证进水端水压不变,当调控的水流量与试样的渗流量达到平衡时,则会在出水端形成一个稳定的水压值。该套试验设备不但可对圆柱体试样进行渗透性、力学特性测试,而且还可以对方柱体试样进行渗透性测试,实现了对岩石实际所处应力、高孔隙水压力环境的真实模拟。实测检验理论技术可行,达到了满意的试验效果。 相似文献
13.
利用大尺寸砂槽试验模型模拟了坝基二维渗流全过程,并着重分析了坝基二维渗流场的变化情况。模型槽内土样渗透变形破坏后,取不同区域土样进行颗粒分析试验。根据渗透变形试验所获得的参数,运用GeoStudio 2007软件对坝基渗流场进行数值分析,所得渗流场分布与物理模型试验结果基本吻合,说明该二维渗流场的物理模型试验结果较为合理。结果表明,渗透破坏主要发生在坝体下渗透路径较短的区域内,而坝基上下游基本未产生渗透变形;产生渗透破坏后,渗流路径发生较大改变,导致渗透破坏区域渗流量大幅增加,加速坝基破坏进程。 相似文献
14.
地下工程渗流排水孔数值模拟的隐式复合单元法 总被引：1，自引：0，他引：1
根据渗流基本原理,提出了排水孔在地下工程中渗流数值模拟的隐式复合单元法。将排水孔隐含于模型网格中,得到排水孔在模型中的数据信息。判断所有排水孔与单元的相对位置,通过修正排水孔所穿过单元的渗透传导矩阵来模拟排水孔的强排水效果,并通过实例对排水子结构法和隐式复合单元法进行了比较。运用编制的三维有限元计算程序对某地下水电站厂房渗流场及排水孔进行了模拟,结果表明,采用隐式复合单元法对排水孔进行模拟是可行的。 相似文献
15.
Effects of temperature and pressure differences on water seepage in breccia were investigated by using the physicochemical seepage instrument.The results show that the relationship of flow and pressure differences can be expressed by a linear equation,and the seepage coefficient is linearly correlated with temperature.The relation-ship between seepage flow and temperature could be described with the linear equation.The constant and tempera-ture seepage coefficient showed a linear relation with pressure.Binary quantitative equation for the seepage flow,temperature and pressure was obtained,and explained with experimental data and theoretical analysis. 相似文献
16.
特低渗透大型露头模型流场测量技术及分布规律研究 总被引：1，自引：0，他引：1
应用电阻率测井原理,建立了一套大型露头模型平面流场测量方法。在此基础上利用特低渗透天然砂岩露头制作大型露头模型进行流场分布规律研究。研究表明,对于平行岩样具有非线性渗流特征的大型露头模型,其井网单元内平面流场特征为注入流体沿主流线方向快速突进,但波及范围较小,且存在不流动区,驱替效果较差。分析了不同驱替倍数下流场的变化规律,对比研究了不同因素对流场以及有效驱动的影响。大型露头模型能直观地反映流场动态的变化过程和驱替效果,能够更好地模拟实际油藏渗流规律。 相似文献
17.
利用电流场的电势微分控制方程与渗流场的流速势微分控制方程的相似性原理,流场法通过检测电流场的分布来确定渗流场,并能快速查明堤坝的管涌渗漏入口。为了更精确地描述土坝管涌的渗流分布及渗流方向,可以测试迎水面和背水面的水平方向与垂直方向的电位差,模拟渗流的矢量分布。从电流密度、电位微分及电位微分绝对值等方面,阐述了矢量流场法模拟渗流矢量分布的基本原理,并以某土石坝渗漏探测为例开展了验证工作。结果显示,矢量流场法可以有效揭示土石坝的渗流等级及渗流方向,结合流场法和矢量流场法探测成果,可为查明土石坝渗漏入口、渗流等级及渗流方向提供新的思路。 相似文献
18.
This paper proposed a numerical formulation for unsaturated flow problems with nonlinear boundaries of seepage face and soil–atmosphere interface via the concept of parabolic variational inequality (PVI) method. A unified unilateral boundary condition was first proposed to represent the conditions on the seepage face and soil–atmosphere interface boundaries within the partial differential equation (PDE) formulation. A PVI formulation mathematically equivalent to the PDE formulation was then proposed, which automatically transforms the flux part of the unified unilateral boundary condition into the natural boundary condition and eliminates the singularity at seepage points. By discretizing the PVI formulation, a finite element procedure together with an iterative algorithm was suggested. An existing experiment of unsaturated flow in a layered hillside and a laboratory test of unsaturated flow through sand flume performed in this study were used to validate the proposed method, with a good agreement between the measured and computed results and a satisfactory balance of mass being maintained during the simulations. The numerical results also indicated that the problem of mesh dependence associated with unsaturated flow simulations is well addressed with the proposed numerical method. Finally, the process of unsaturated flow in a soil slope with layers of horizontal drains subjected to rainfall/evaporation was further examined. The numerical results reveal that the deployment of drains in a soil slope can significantly lower the pore water pressure around the drains, with the bottom layer drains being most effective in controlling the seepage flow. 相似文献
19.
Digital image processing technology can objectively reflect the surface roughness of coal and rock mass fractures and turn physical properties such as fluctuation height to physical data of the rock fracture surface to be used for numerical analyses; thus, it can effectively be applied to the seepage flow analysis of rock fractures. First, clear digital images of the fracture surface height are obtained under the same camera conditions, and then characteristic function values specific to various structure are normalized. Subsequently, the fluctuation height distribution of the rock surface is restored according to the measured fluctuation heights of local points. Finally, according to the surface fluctuation of fractures, invasive restructuring is carried out for three-dimensional fractures in the same coordinate system. Obtained physical parameters on the three-dimensional fractures of the rock are inputted into the COMSOL Multiphysics software to obtain the characteristic three-dimensional model of the rock fracture surface. The numerical analysis results are compared with experimental data on fracture seepage obtained from a seepage coupling true triaxial test system, and the relevance between the simulated result and the physical experiment is higher than 90%, which confirms that the integration of the digital image technology and the numerical analysis method can effectively simulate seepage in rough fractures. The hydraulic gradient of rough fractures and seepage velocity are also consistent with Forchheimer flow characteristics. 相似文献
20.
Numerical simulation of groundwater flowing to horizontal seepage wells under a river 总被引：6，自引：0，他引：6
A horizontal seepage well, consisting of an interconnected vertical well, galleries, chambers and small-diameter radiating
bores, is used to acquire relatively clean water that has been filtered through natural alluvial deposits in a riverbed. It
has wide application, especially in arid and semi-arid areas. The lack of calculation formulae or models for horizontal seepage
wells, up until now, has resulted in several false applications. Based on the analysis of groundwater flow characteristics,
it has been concluded that several flow regimes coexist and hydraulic head loss exists in the horizontal seepage well. To
avoid the difficulty of confirming the flux or head distribution in such a complex system, the model boundary of the whole
horizontal seepage well has been moved to that of just the vertical well, and the well-aquifer system was treated as a heterogeneous
medium, where the horizontal seepage well itself is a highly permeability medium. A mathematical model has been developed,
based on the coupled seepage-pipe flow, by the introduction of equivalent hydraulic conductivity according to different flow
regimes. Then a three-dimensional finite difference numerical model, based on the mathematical model, was developed and applied
to a horizontal seepage well in China. The numerical model verified the groundwater flow characteristics of the horizontal
seepage well.
An erratum to this article can be found at 相似文献