Discontinuous Galerkin methods for advective transport in single-continuum models of fractured media     

Birgitte Eikemo  Knut-Andreas Lie  Geir Terje Eigestad  Helge K. Dahle 《Advances in water resources》2009

Accurate simulation of flow and transport processes in fractured rocks requires that flow in fractures and shear zones to be coupled with flow in the porous rock matrix. To this end, we will herein consider a single-continuum approach in which both fractures and the porous rock are represented as volumetric objects, i.e., as cells in an unstructured triangular grid with a permeability and a porosity value associated with each cell. Hence, from a numerical point of view, there is no distinction between flow in the fractures and the rock matrix. This enables modelling of realistic cases with very complex structures. To compute single-phase advective transport in such a model, we propose to use a family of higher-order discontinuous Galerkin methods. Single-phase transport equations are hyperbolic and have an inherent causality in the sense that information propagates along streamlines. This causality is preserved in our discontinuous Galerkin discretization. We can therefore use a simple topological sort of the graph of discrete fluxes to reorder the degrees-of-freedom such that the discretized linear system gets a lower block-triangular form, from which the solution can be computed very efficiently using a single-pass forward block substitution. The accuracy and utility of the resulting transport solver is illustrated through several numerical experiments.  相似文献   

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谢建涛  郝金明邱 璇 《大地测量与地球动力学》2013,33(6):90-93

??????RTK??????λ?У???????????ο?????????????????????????????????????????????????????????λ????????????????????????????LIM???????????????????????????????????????????CORS?????????ο??????????????????????????????????????LIM???????徫?????????1~2 cm??  相似文献   

沙地小麦凋落物的分解残留物中营养元素的动态线性分析     

赵学勇  张铜会  张志坚 《中国沙漠》1999,19(Z1):99-102

在测定科尔沁沙地小麦凋落物分解率的基础上,对分解残留物中的N、P、Ca和S等元素含量进行了测定与分析。结果表明,4种元素随着分解的进行呈现增加的趋势。如果把分解时间用土壤温度大于0℃的天数来表示,对应的N、P、Ca和S元素含量变化除P之外,其它3种元素含量与分解天数之间的相关系数r均大于0.9,表现较好的线性关系,为揭示作物和土壤间养分元素的交换提供了便利的方法。但在分解测定的头两次取样和最后两次取样之间,元素含量变化与分解天数的线性关系较差,这是由于各种元素在小麦凋落物中初始含量的差异,导致了元素在分解始末变化区间的不同。  相似文献   

地下水超采区水位长趋势动态分析   总被引：7，自引：1，他引：6  

张素欣  刘耀炜  陆明勇  张子广 《地震》2007,27(4):51-58

地下水多年过量开采水位持续下降, 不仅在观测资料中叠加了大量的疑似地震前兆, 严重地压低了来自孕震体的信息, 而且使正常的地震长、 中、 短周期变化背景扭曲, 前兆异常更加难辨。 本研究采用“线性拟合去趋势方法”对水位多年观测资料进行了分析。 分析结果表明, 线性拟合去趋势后水位10年左右的准周期结构清楚, 能有效地排除地下水超采的影响, 突出正常趋势变化背景, 放大潮汐信息量, 便于识别地震前兆。  相似文献   

蒙城台地电场资料分析   总被引：3，自引：0，他引：3  

郑兆苾  汪雪泉 《地震》2005,25(2):41-47

通过对安徽省蒙城台2002年地电场分钟值数据的处理分析, 结果认为该台可以清晰地记录到大地电场的正常日变化、 电磁暴; 同一方向长短极距的变化基本同步; NS向、 EW向与NW向的比测误差基本正常; 拟合极化方向角在静日和有电磁暴时, 在N80°W～N100°W内摆动, 较稳定, 有干扰和雷电时极化方向明显偏转; 大地电场矢量方向角α变化大。 受降雨、 外线接触不良、 仪器工作状况不佳的影响, 少数数据质量不好, 通过改进, 还可以进一步提高观测质量。  相似文献   

多步法快速射线追踪与圆台型高精度走时外插计算          下载免费PDF全文

梁全  毛伟建  李武群  欧阳威  钱忠平 《地球物理学报》2019,62(11):4367-4377

为更好地适应复杂构造的地震偏移成像,本文提出了一套快速射线追踪算法和一种高精度的走时外插计算方法.采用线性多步法的预测-校正公式求解射线追踪方程组,与传统的四阶Runge-Kutta法相比,提高了计算效率.在网格节点上的走时计算中,应用一种基于圆台的外插方法,该方法以射线的方向为轴确定圆台,将轴上的走时外插到圆台内的网格节点上.与传统的矩形体外插方法相比,圆台走时外插方法提高了计算精度,且具有更好的稳定性.另外,该方法利用稀疏分布的射线即可获得高精度的走时表,节省计算量,对复杂构造的偏移成像非常有利,尤其是三维偏移.最后通过逆散射偏移成像算例,验证了算法的有效性和适用性.  相似文献   

Long-term coastal erosion assessment along the coast of Karnataka,west coast of India     

K.Sowmya  M.Dhivya Sri  Aparna S.Bhaskar  K.S.Jayappa 《国际泥沙研究》2019,34(4):335-344

Coastal areas are always under frequent threat from various natural processes and man-induced activities. Coastal erosion is recognized as the permanent loss of land along the shoreline resulting in the transformation of the coast. The current study focuses on long-term coastal erosion analysis of the entire Karnataka coast using Remote Sensing, Geographical Information System (GIS), Linear Regression Rate (LRR), and End Point Rate (EPR) techniques. Analysis of 26 (1990 to 2016) years of erosion using Landsat images by the use of the Digital Shoreline Analysis System (DSAS) tool has been done. The results show a high erosion rate at Ullal during this period (LRR -1.3m/yr) and accretion at Devbagh (LRR 3.2 m/yr). The southern Karnataka coast faces severe erosion especially at Ullal, where the settlement is high. At Thanirbhavi, Mukka, Kota, and Om Beaches erosion also is noticed. Both anthropogenic activities like ports, seawalls, breakwaters, etc. and natural processes like long shore drift, seasonal variation, etc. are factors affecting the shoreline change along the Karnataka coast.  相似文献   

Photogravitational magnetic-binary problem with oblateness and belt of material points     

《New Astronomy》2022

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Mid-latitude atmospheric responses to heat and vorticity forcing using a linear baroclinic model   总被引：1，自引：0，他引：1       下载免费PDF全文

QIU Shuang  FANG Jiabei  YANG Xiuqun 《气象科学》2014,34(2):149-161

Based on diagnostic analysis of reanalysis data for 58-year, the distribution characteristics of decadal variability in diabatic heating, transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature (SST) anomalies over the North Pacific, as well as their relationship with anomalous atmospheric circulation have been investigated in this paper. A linear baroclinic model(LBM) was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies, and then to compare relative roles of different kinds of forcing in terms of geopotential height responses. The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic. The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow, as well as to the vertical profile of heating. The response to the idealized deep heating over the eastern North Pacific, mimicking the observed heating anomaly, is baroclinic. The atmospheric response to the mid-latitude vorticity forcing is always barotropic, resulting in a geopotential low that is in phase with the forcing. The atmospheric responses to the realistic heat and vorticity forcing show the similar results, suggesting that diabatic heating, transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies.  相似文献