Improved numerical solvers for implicit coupling of subsurface and overland flow     

《Advances in water resources》2014

Due to complex dynamics inherent in the physical models, numerical formulation of subsurface and overland flow coupling can be challenging to solve. ParFlow is a subsurface flow code that utilizes a structured grid discretization in order to benefit from fast and efficient structured solvers. Implicit coupling between subsurface and overland flow modes in ParFlow is obtained by prescribing an overland boundary condition at the top surface of the computational domain. This form of implicit coupling leads to the activation and deactivation of the overland boundary condition during simulations where ponding or drying events occur. This results in a discontinuity in the discrete system that can be challenging to resolve. Furthermore, the coupling relies on unstructured connectivities between the subsurface and surface components of the discrete system, which makes it challenging to use structured solvers to effectively capture the dynamics of the coupled flow. We present a formulation of the discretized algebraic system that enables the use of an analytic form of the Jacobian for the Newton–Krylov solver, while preserving the structured properties of the discretization. An effective multigrid preconditioner is extracted from the analytic Jacobian and used to precondition the Jacobian linear system solver. We compare the performance of the new solver against one that uses a finite difference approximation to the Jacobian within the Newton–Krylov approach, previously used in the literature. Numerical results explores the effectiveness of using the analytic Jacobian for the Newton–Krylov solver, and highlights the performance of the new preconditioner and its cost. The results indicate that the new solver is robust and generally outperforms the solver that is based on the finite difference approximation to the Jacobian, for problems where the overland boundary condition is activated and deactivated during the simulation. A parallel weak scaling study highlights the efficiency of the new solver.  相似文献   

西南省域地震灾害耦合因素分析     

吴微微 《地震地磁观测与研究》2014,(1):92-96

利用西南震害资料,对西南省域（云南、四川、重庆、西藏、贵州）在一定时空尺度上M≥5．0历史地震事件活动水平及震害特征进行系统分析,找出地震灾害（包括人员伤亡、经济损失、次生灾害等）的时间发展特征、空间分布特征和强度分级特征;研究地震灾害与西南区域人口分布、经济水平、地形地貌、人文因素之间的耦合关系,为进一步减轻、减少地震灾害应急处置的不确定性和风险性提供有效建议。  相似文献   

Impacts of boundary layer parameterization schemes and air-sea coupling on WRF simulation of the East Asian summer monsoon   总被引：2，自引：0，他引：2  

WANG ZiQian  DUAN AnMin  WU GuoXiong 《中国科学:地球科学(英文版)》2014,57(7):1480-1493

The planetary boundary layer(PBL)scheme in the regional climate model(RCM)has a significant impact on the interactions and exchanges of moisture,momentum,and energy between land,ocean,and atmosphere;however,its uncertainty will cause large systematic biases of RCM.Based on the four different PBL schemes(YSU,ACM2,Boulac,and MYJ)in Weather Research and Forecasting(WRF)model,the impacts of these schemes on the simulation of circulation and precipitation during the East Asian summer monsoon(EASM)are investigated.The simulated results of the two local turbulent kinetic energy(TKE)schemes,Boulac and MYJ,are more consistent with the observations than those in the two nonlocal closure schemes,YSU and ACM2.The former simulate more reasonable low-level southwesterly flow over East China and west pacific subtropical high(WPSH)than the latter.As to the modeling of summer monsoon precipitation,both the spatial distributions and temporal evolutions from Boulac and MYJ are also better than those in YSU and ACM2 schemes.In addition,through the comparison between YSU and Boulac experiments,the differences from the results of EASM simulation are more obvious over the oceanic area.In the experiments with the nonlocal schemes YSU and ACM2,the boundary layer mixing processes are much stronger,which lead to produce more sea surface latent heat flux and enhanced convection,and finally induce the overestimated precipitation and corresponding deviation of monsoon circulation.With the further study,it is found that the absence of air-sea interaction in WRF may amplify the biases caused by PBL scheme over the ocean.Consequently,there is a reduced latent heat flux over the sea surface and even more reasonable EASM simulation,if an ocean model coupled into WRF.  相似文献   

非均质土中桩端扩散虚土桩法的桩基纵向振动研究     

杨冬英  丁海平 《岩土力学》2014,35(Z1):311-318

根据桩端土应力扩散的规律,建立了桩端扩散虚土桩模型。基于该模型对非均质土中桩-土纵向耦合振动进行研究。利用复刚度传递多圈层平面应变模型,得到桩与虚土桩桩侧土的剪切复刚度。结合边界条件、初始条件和连续条件,对扩散虚土桩和实体桩动力方程从底层往顶层逐层进行求解,得到桩顶动力响应的频域解析解和时域半解析解。通过对桩端扩散虚土桩扩散角、扩散层厚度、桩侧土非均质性和桩长的影响进行计算分析,得到基于扩散虚土桩法桩-土纵向振动响应特性。研究结论可为桩基础动力设计和动态检测提供理论依据。  相似文献   

多场耦合作用下岩体裂隙扩展演化关键问题研究     

刘泉声  刘学伟 《岩土力学》2014,299(2):305-321

裂隙岩体热-水-应力（THM）耦合是目前研究的热点和难点。首先总结了裂隙岩体多场耦合的机制、模型、方法及研究内容,并通过分析裂隙对THM耦合的重要控制作用,提出了在THM耦合中考虑裂隙网络扩展演化及模拟的关键问题,同时指出了研究的3个关键点：（1）建立考虑裂隙网络演化的耦合模型;（2）裂隙扩展的数值模拟方法;（3）THM耦合及岩体变形、失稳全过程的数值模拟算法。随后通过对模拟多场耦合和裂隙扩展数值方法的归类比较,重点论述了目前适用于模拟多场耦合下裂隙扩展模拟的各种数值方法（包括有限单元法、无单元法、单位分解法、离散单元法、岩石破裂过程分析方法和数值流形方法）的优缺点,并通过对比研究,推荐采用数值流形方法（NMM）来实现对关键问题的模拟研究。最后,对研究思路和难点进行了初步探讨。  相似文献   

Coupling between landslides and eroding stream channels reconstructed from spruce tree rings (examples from the Carpathians and Sudetes – Central Europe)          下载免费PDF全文

Małgorzata Wistuba  Ireneusz Malik  Krzysztof Wójcicki  Patrycja Michałowicz 《地球表面变化过程与地形》2015,40(3):293-312

The analysis of the positive feedback between landslides and erosion requires determination of the precise temporal and spatial relations between events of colluvium delivery and fluvial erosion. In our study we use decennial datasets on the occurrence of landsliding and erosion achieved through dendrochronological methods. Four sites covering areas of landslide slopes and adjacent valley floors with stream channels were studied. Landsliding on slopes was dated from the tree‐ring eccentricity developed in stems tilted due to bedrock instability. Erosion in channels was dated using the wood anatomy of roots exposed by erosion of the soil cover. Analysis of the temporal relations between dated landsliding, erosion and precipitation record has revealed that two types of repeating sequences can be observed: (1) rainfall → landsliding → erosion; (2) rainfall → erosion → landsliding. These sequences are an indication of the occurrence of slope‐channel positive feedback in the sites studied. In the first type, landsliding triggered by rainfall delivers colluvia into the valley floor and causes its narrowing, which in turn causes increased erosion. In the second type erosion triggered by rainfall disturbs the slope equilibrium and causes landsliding. Landsliding and erosion, once triggered by precipitation, can occur alternately in years with average precipitation and reinforce one another. Bidirectional coupling between landsliding and channel erosion was shown notably through the effects of channel shifting and forced sinuosity and by increased erosion of the slopes opposite the active landslides. Observations also suggest that the repetition of sequences described over longer periods of time can lead to a general widening of the valley floor at the expense of slopes and to a gradual change of the valley cross‐profile from narrow, V‐shaped into a wide flat‐bottomed. Thus landsliding–erosion coupling/positive feedback was recognized as an important factor shaping hillslope–valley topography of the mid‐mountain areas studied. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

松辽盆地北部干热岩开发水热产出预测     

李正伟  张延军  郭亮亮  金显鹏 《吉林大学学报(地球科学版)》2015,45(4):1189-1197

干热岩是一种分布广泛且储量巨大的清洁能源,在干热岩开发的前期,合理预测场地的水热产出能力具有重要的意义.笔者根据松辽盆地北部莺深2井的实际地质资料,以石油压裂设计软件FRACPRO为手段,进行了压裂模拟.根据模拟得到裂缝几何形态与孔、渗的性质,通过自编程序修正水热耦合地质模型中的单元参数,并利用TOUGH2软件模拟换热过程.模拟结果显示:在本文采取的压裂方式下,该地区单条裂缝的最大生产流速为8 kg/s,系统流动阻抗由初始的0.74 MPa/(kg·s) 增加为第10年的2.72 MPa/(kg·s);系统运行10 a后,生产温度降低了5.5 ℃,系统的平均产热功率为2 930 kJ/s.通过人工改造,改善了天然储层的渗流能力,获得了持续稳定的水热产出,证明储层改造方式科学合理,但如何提高热储的质量生产流速仍需进一步研究.  相似文献   

东北振兴以来吉林省四化发展的协调性研究   总被引：5，自引：3，他引：2  

尹鹏  刘继生  陈才 《地理科学》2015,35(9):1101-1108

运用耦合协调度模型、探索性空间数据分析和障碍度模型,判别东北振兴以来吉林省四化发展的协调性。结果表明：吉林省四化发展水平具有时间波动性和空间非均衡性,仅有农业现代化水平呈现递减态势,工业化和城镇化的空间分异不断缩小,信息化和农业现代化的空间分异逐渐增大;四化发展处于低水平耦合阶段,非同步性特征明显,中部城市群和东部沿边地区耦合度较高,西部内陆地区耦合度低,包括严重失调、中度失调和轻度失调三种类型;四化协调水平相似地区由离散分布向弱集聚状态转变,中部长吉、东部延边和通化地区是四化协调的热点或次热点,热点区县域不断减少,冷点区县域逐渐增加;2003年四化协调的前5项障碍指标是三产产值比重>人均GDP>非农人口比重>万人医院和卫生机构床位数>邮电业务指数,2012年前5项障碍指标是二产产值比重>二产从业人员比重>人均工业总产值>农业地均经济产出>农业劳均农产品产量,子系统障碍度大小排序为城镇化>农业现代化>工业化>信息化。最后,从区域战略政策、经济产业基础和自然地理环境探讨四化协调演化的驱动机制,并提出相应政策建议。  相似文献   

江西省人口与经济发展时空耦合研究   总被引：4，自引：3，他引：1  

吴连霞  赵媛  马定国  管卫华 《地理科学》2015,35(6):742-748

以区域人口与经济发展的相互作用关系为主线,以江西省91个县（市、区）为研究对象,运用灰色关联法（GRA）,选取人口系统6个指标和经济系统5个指标,构建江西省人口与经济耦合关联模型,定量评判人口系统与经济系统交互作用的关联耦合程度,并将经济增长阶段理论及区域产业结构演进理论与耦合度相联系,分析人口与经济发展的耦合特征。研究结果表明：江西省各县（市、区）可以划分为低水平耦合区、拮抗型耦合区、磨合型耦合区和协调型耦合区等4种类型。全省人口与经济耦合度空间分布以低水平耦合类型为主,拮抗类型为辅。耦合度分布基本上符合南、北空间分异的规律,空间分布呈现“+”字型,以浙赣线为横轴,昌九线为纵轴,交汇于南昌市。在时间序列上,江西省人口与经济耦合发展表现出明显的波动性和阶段性,逐渐由低水平时期向拮抗阶段过渡。  相似文献   

塔里木河流域农牧资源与农牧经济耦合关系     

田童  刘新平  赵俊  刘雨萌 《中国沙漠》2015,35(5):1382-1387

通过构建农牧资源与农牧经济协调发展耦合评价指标体系,采用耦合度模型评价了2004-2011年塔里木河流域农牧资源与农牧经济耦合发展水平,并提出塔里木河流域农牧资源与农牧经济协调发展的对策建议。结果表明:(1)塔里木河流域农牧资源系统指数呈现稳中有升的态势,总体升势较为平稳,未出现较大波动。(2)西部大开发战略的顺利实施、对口援疆项目的落地,使塔里木河流域农牧经济得到快速发展,农牧经济系统指数实现较大幅度的增长。(3)农牧资源与农牧经济耦合发展水平上升趋势明显,但是协调度不太高,农牧经济的快速发展使农牧资源保护的难度持续增大,协调发展压力仍然较大。  相似文献