Solving the Buckley–Leverett equation with gravity in a heterogeneous porous medium     

E.F. Kaasschieter 《Computational Geosciences》1999,3(1):23-48

Immiscible two‐phase flow in porous media can be described by the fractional flow model. If capillary forces are neglected, then the saturation equation is a non‐linear hyperbolic conservation law, known as the Buckley–Leverett equation. This equation can be numerically solved by the method of Godunov, in which the saturation is computed from the solution of Riemann problems at cell interfaces. At a discontinuity of permeability this solution has to be constructed from two flux functions. In order to determine a unique solution an entropy inequality is needed. In this article an entropy inequality is derived from a regularisation procedure, where the physical capillary pressure term is added to the Buckley‐Leverett equation. This entropy inequality determines unique solutions of Riemann problems for all initial conditions. It leads to a simple recipe for the computation of interface fluxes for the method of Godunov. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

THE FORMULATION OF FIDELITY SCHEMES OF PHYSICAL CONSERVATION LAWS AND IMPROVEMENTS ON A TRADITIONAL SPECTRAL MODEL OF BAROCLINIC PRIMITIVE EQUATIONS FOR NUMERICAL PREDICTION     

钟青 《Acta Meteorologica Sinica》1999,(2)

In this paper,two formulation theorems of time-difference fidelity schemes for generalquadratic and cubic physical conservation laws are respectively constructed and proved,with earliermajor conserving time-discretized schemes given as special cases.These two theorems can providenew mathematical basis for solving basic formulation problems of more types of conservative time-discrete fidelity schemes,and even for formulating conservative temporal-spatial discrete fidelityschemes by combining existing instantly conserving space-discretized schemes.Besides.the twotheorems can also solve two large categories of problems about linear and nonlinear computationalinstability.The traditional global spectral-vertical finite-difference semi-implicit model for baroclinicprimitive equations is currently used in many countries in the world for operational weatherforecast and numerical simulations of general circulation.The present work,however,based onTheorem 2 formulated in this paper,develops and realizes a high-order total energy conservingsemi-implicit time-difference fidelity scheme for global spectral-vertical finite-difference model ofbaroclinic primitive equations.Prior to this,such a basic formulation problem remains unsolved forlong,whether in terms of theory or practice.The total energy conserving semi-implicit schemeformulated here is applicable to real data long-term numerical integration.The experiment of thirteen FGGE data 30-day numerical integration indicates that the newtype of total energy conserving semi-implicit fidelity scheme can surely modify the systematicdeviation of energy and mass conserving of the traditional scheme.It should be particularly notedthat,under the experiment conditions of the present work,the systematic errors induced by theviolation of physical laws of conservation in the time-discretized process regarding the traditionalscheme designs(called type Z errors for short)can contribute up to one-third of the totalsystematic root-mean-square(RMS)error at the end of second week of the integration and exceedone half of the total amount four weeks afterwards.In contrast,by realizing a total energyconserving semi-implicit fidelity scheme and thereby eliminating corresponding type Z errors,roughly an average of one-fourth of the RMS errors in the traditional forecast cases can be reducedat the end of second week of the integration,and averagely more than one-third reduced at integraltime of four weeks afterwards.In addition,experiment results also reveal that,in a sense,theeffects of type Z errors are no less great than that of the real topographic forcing of the model.The prospects of the new type of total energy conserving fidelity schemes are very encouraging.  相似文献   

筛选法——一种矿产预测新方案的概念和原理          下载免费PDF全文

陈明  范继璋 《地球科学》1999,24(1):79-82

矿产资源体的形成受一定的成矿条件和控矿因素约束．这些约束条件可以分为成矿必要条件和成矿充分条件两大类．必要条件决定了资源体能否形成,充分条件决定了资源体的具体经济指标．利用某个成矿必要条件可把研究区内的所有单元分成“可能成矿单元”和“非成矿单元”两大部分．通过多个成矿必要条件的逐步筛选,又可从“可能成矿单元”中进一步提取“成矿单元”,从而实现矿产资源的定性预测．把所有单元通过如上所述的筛选过程并提取“成矿单元”的方法称为“筛选法”（ｓｉｆｔｉｎｇｓｃｈｅｍｅ）．在模型矿床存在的条件下,可通过充分条件在地质变量和资源量之间进行数字建模,并对未知“成矿单元”进行定量评价．研究表明,筛选法有可能为采矿企业提供更可靠的找矿靶区．  相似文献   

26000kN垂直静载荷试验设计方案及成果初探     

叶建辉  黄清和 《水文地质工程地质》1999,26(4):13-15

本文通过在漳州某电厂实施２６０００ｋＮ基桩垂直静载荷试验项目,在此对国内最大吨位静载荷试验的组织设计方案和试验方法（锚桩法）进行介绍,并简介试验成果,以供同行参考,并提出宝贵意见。  相似文献   

热带海洋SSTA的POP中性预测方案     

李丽平  王盘兴  吴洪宝 《南京气象学院学报》1999,22(3):360-366

用主振荡型（ Ｐ Ｏ Ｐ）方法分析了热带洋区月平均海表温度异常（ Ｓ Ｓ Ｔ Ａ）。结果表明,最重要的 ４ 个传播型 Ｐ Ｏ Ｐ对与 Ｅｌ Ｎｉｎｏ／ Ｌａ Ｎｉｎａ 事件关系密切,说明这类事件具有复杂的时空结构。在此基础上,给出了一个能定量地综合多个传播型 Ｐ Ｏ Ｐ对作用的 Ｐ Ｏ Ｐ中性预测方案。非独立样本和独立样本试验表明,它具有 ４ 个月的预测时效,且其预测能力在 Ｓ Ｓ Ｔ 强异常的 Ｅｌ Ｎｉｎｏ、 Ｌａ Ｎｉｎａ 事件阶段强于弱异常的非 Ｅｌ Ｎｉｎｏ／ Ｌａ Ｎｉｎａ 事件阶段。  相似文献   

华南区域短期气候模式产品时间过滤方案及实例分析   总被引：1，自引：1，他引：0  

阎敬华 《热带气象学报》1999,15(3):213-220

用尺度分离方法分析了短期气候预测序列中所包含的各种尺度的过程,建立了不同尺度变化的过滤、提取方法;分析讨论了各种过滤序列所具有的气候意义和重要程度;用模拟实例分析了所提出和使用的尺度分离方法的有效性及模式的性能  相似文献   

基于优化有限差分和混合吸收边界条件的三维VTI介质声波和弹性波数值模拟          下载免费PDF全文

徐世刚  刘洋 《地球物理学报》2018,61(7):2950-2968

传统有限差分系数是通过泰勒级数展开求取的,这样导致所计算的频散曲线在大波数区域会产生较强的数值误差.针对二阶空间偏导数的显式有限差分离散,本文发展了一种新的优化差分系数方法：首先将泰勒级数展开与多点采样方法结合应用于空间频散关系,基于最大范数建立直观有效的优化目标函数,采用Remez算法求解该目标函数,从而获得最优化差分系数.利用优化有限差分方法求解三维垂直对称轴横向各向同性（VTI）介质中的声波和弹性波方程.另外,本文将二维混合吸收边界条件推广到三维VTI介质中,用于吸收人工截断边界反射;基于各向异性特征,合理调整了边界区域的速度值来提高吸收效果.考虑到三维情况下计算效率的问题,本文波场外推过程中采用图形处理器（GPU）取代传统的中央处理器（CPU）.数值精度分析表明,相比较于传统的泰勒级数展开方法,优化有限差分方法在大波数区域对频散误差的压制效果更明显.在三维均匀和修改的Hess VTI模型中的数值模拟实验证明了本文方法具有更高的精度与效率,混合吸收边界条件在三维VTI介质中具有良好的边界吸收效果.  相似文献   

太原基准地震台高清监控系统建设     

何佳  梁静  李云  许振鹏  任瑞国 《山西地震》2019,(2):39-41

为落实安全生产工作要求,太原基准地震台急需建设一套高清视频监控系统。文章着重介绍了高清监控系统的建设思路、设计方案、系统功能,该系统可为进一步增强台站安全技防能力、解决当前地震台站安全防范问题提供技术支持,也为同类台站提供安防建设思路。  相似文献   

晋冀蒙交界及附近地区小极距井下地电阻率观测装置设计   总被引：1，自引：1，他引：0  

肖武军  解滔  张尧 《中国地震》2019,35(1):134-143

为提升2022年北京冬奥会期间地电阻率测项的震情保障能力,将对晋冀蒙交界及附近区域的宝昌、集宁、阳原、大同、代县、临汾、通州和平谷8个台站在原有观测基础上增加具有全空间性质的小极距井下地电阻率观测。本文根据台站钻孔岩芯剖面和电测深数据反演测区水平层状电性结构,利用介质对地电阻率观测的影响系数方法,计算影响系数随极距和埋深的变化,选择合适的极距和埋深,使浅层介质对地电阻率观测的影响尽可能小,使目标层位对观测的贡献尽可能大,减少浅层介质对观测的影响。由此得出了各台站观测极距及埋深等装置系数,在此基础上完成了8个台站观测装置的方案设计。  相似文献   

考虑强震激励的某核岛厂房非岩性地基不同处理方案的对比研究          下载免费PDF全文

尹训强  刘小蒙  王桂萱 《地震工程学报》2017,39(3):443-451

如何选取非岩性地基的处理方案对于不满足抗震适应性要求的核岛厂房地基而言具有重要的工程实用价值。结合国内某内陆核电不符合抗震适应性要求的实际厂址条件,给出地基处理方案评价的数值计算模型及分析过程。首先针对该核电工程实际项目,提出嵌岩桩、CFG桩及水泥土搅拌桩三种地基预处理方案,并以规范法验证处理后地基的承载力要求;进而通过建立非岩性地基条件下的桩-土-结构动力相互作用计算模型来综合考虑各方案对核岛厂房的地震响应影响,其中通过引入黏性人工边界和能量传递边界模拟无限地基辐射阻尼效应,采用等效线性法描述近场地基非线性特征,并基于上述有限元模型以全耦合方式考虑群桩效应的影响;最后从满足厂址地基适应性和经济效益两方面进行综合评价,给出针对本工程的最佳设计方案。该分析方法及研究成果可为类似条件下的核岛厂房非岩性地基处理方案的比选问题提供借鉴与参考。  相似文献