Theoretical and numerical analyses of convective instability in porous media with upward throughflow     

Chongbin Zhao  B. E. Hobbs  H. B. Mühlhaus 《国际地质力学数值与分析法杂志》1999,23(7):629-646

Exact analytical solutions have been obtained for a hydrothermal system consisting of a horizontal porous layer with upward throughflow. The boundary conditions considered are constant temperature, constant pressure at the top, and constant vertical temperature gradient, constant Darcy velocity at the bottom of the layer. After deriving the exact analytical solutions, we examine the stability of the solutions using linear stability theory and the Galerkin method. It has been found that the exact solutions for such a hydrothermal system become unstable when the Rayleigh number of the system is equal to or greater than the corresponding critical Rayleigh number. For small and moderate Peclet numbers (Pe ⩽ 6), an increase in upward throughflow destabilizes the convective flow in the horizontal layer. To confirm these findings, the finite element method with the progressive asymptotic approach procedure is used to compute the convective cells in such a hydrothermal system. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

2004年阳江4.9级地震破裂方位角研究   总被引：2，自引：0，他引：2  

叶秀薇  闻则刚  邱奕超  杨马陵  刘吉平 《大地测量与地球动力学》2006,26(4):102-106

在一维有限移动震源模式下,根据地震波传播过程中的多普勒效应利用S波或P波拐角频率的方向性来确定地震破裂面的方法,计算了2003年11月~2005年10月阳江地区13次ML≥2.5地震的发震断层走向,结果显示:利用S波、P波拐角频率得到的2004年9月阳江4.9级地震破裂方位角分别为167°和166°,地震序列以NNW为主要破裂方向。  相似文献   

川滇次级地块震源机制解类型与一致性参数   总被引：18，自引：3，他引：15       下载免费PDF全文

程万正  阮祥  张永久 《地震学报》2006,28(6):561-573

根据P波、S波的振幅并结合部分记录清晰的P波初动资料,求得1994——2005年川滇地区4个次级地块,即川青地块、雅江地块、川中地块和滇中地块2.5级以上有良好地震波记录的925次地震的震源机制解. 结合已取得的中强地震的震源机制解资料,研究了上述4个次级地块的应力场特征及震源断层的错动类型. 其P轴优势方位分布:川青地块为EW方向,雅江地块、川中地块、滇中地块为ESE或SE方位. 根据大量震源机制解资料, 编程计算了各地块的平均应力张量, 即主应力sigma;1, sigma;2, sigma;3的方向. 定义了单个震源机制解的力轴与平均应力张量的差异, 或称震源机制解的一致性参数, 进而分析了川滇4个次级地块的值和震源断层错动类型的分布及随时间的变化. 通过次级地块大量区域小震震源机制解的测定,可以给出动态应力场和震源断层错动方式的变化信息.   相似文献   

重力式码头CAD系统开发的荷载解决方案     

夏运强  陈兆林 《海岸工程》2006,25(1):6-14

针对重力式码头CAD系统开发中存在的设计荷载处理的技术难题,提出了一种切实可行的计算机解决方案,并提供了CAD系统常用的数据接口技术。该方案有较强的应用价值,可作为开发各类重力式码头CAD系统的借鉴。  相似文献   

Generalized de Sitter solution in multi-dimensional cosmology with static internal spaces     

A. Zhuk 《Astronomische Nachrichten》1995,316(5):269-274

A multi-dimensional cosmological model with space-time consisting of n(n ≥ 2) Einstein spaces M_i is investigated in the presence of a cosmological constant λ and a homogeneous minimally coupled free scalar field. A generalized de Sitter solution was found for λ > 0 and a Ricci-flat external space for the case of static internal spaces with fine tuning of parameters.  相似文献   

Analytical and statistical approach for evaluating the effects of a river barrage on river–aquifer interactions          下载免费PDF全文

Yun‐Yeong Oh  Se‐Yeong Hamm  Heesung Yoon  Gyoo‐Bum Kim 《水文研究》2016,30(21):3932-3948

The construction of a river barrage can increase groundwater levels upstream of the barrage during the rainy season. Analytical and statistical approaches were applied to evaluate the relationship between groundwater and river water at the Changnyeong–Haman river barrage in Korea using time series data of water level and electrical conductivity from June 2011 to September 2014. An artificial neural network based time series model was designed to filter out the effect of rainfall from the groundwater level data in the study area. Aquifer diffusivity and river resistance were estimated from the analytical solution of a one‐dimensional unit step response function by using the filtered groundwater level data. River resistance increased in response to groundwater level fluctuations. Cross‐correlation analyses between the groundwater and the river water showed that the lag time increased during the observation period for both the water level and the electrical conductivity while the cross‐correlation function declined for the same period. The results indicated that a constant river stage maintained at the river barrage can weaken the hydrologic stress and reduce the exchange of material between the river and the adjacent aquifer because of the deposition of fine sediment on the river bottom and walls. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Time–space fractional governing equations of one‐dimensional unsteady open channel flow process: Numerical solution and exploration          下载免费PDF全文

Ali Ercan  M. Levent Kavvas 《水文研究》2017,31(16):2961-2971

Although fractional integration and differentiation have found many applications in various fields of science, such as physics, finance, bioengineering, continuum mechanics, and hydrology, their engineering applications, especially in the field of fluid flow processes, are rather limited. In this study, a finite difference numerical approach is proposed to solve the time–space fractional governing equations of 1‐dimensional unsteady/non‐uniform open channel flow process. By numerical simulations, results of the proposed fractional governing equations of the open channel flow process were compared with those of the standard Saint‐Venant equations. Numerical simulations showed that flow discharge and water depth can exhibit heavier tails in downstream locations as space and time fractional derivative powers decrease from 1. The fractional governing equations under consideration are generalizations of the well‐known Saint‐Venant equations, which are written in the integer differentiation framework. The new governing equations in the fractional‐order differentiation framework have the capability of modelling nonlocal flow processes both in time and in space by taking the global correlations into consideration. Furthermore, the generalized flow process may possibly shed light on understanding the theory of the anomalous transport processes and observed heavy‐tailed distributions of particle displacements in transport processes.  相似文献   

A 3—Dimensional baroclinic circulation model of the tropical and northern Pacific     

Cai Yi  Li Yu-xiang 《中国海洋湖沼学报》1997,15(1):70-79

A primitive equation 3-dimensional baroclinic ocean model without the rigid-lid approximation is described. The horizontal resolution is 2.5°×2° and the vertical variations of the velocity components are resolved by 6 layers. In order to increase the allowable integration time step which is constrained by stability requirements, the vertically integrated continuity equation is linearized and both the pressure gradient terms and the Coriolis terms in the momentum equations are finite-differenced semi-implicitly. The model is applied to simulate the circulation as well as the free surface elevation and temperature patterns in the tropical and northern Pacific Ocean in both summer and winter using the wind and temperature data at the 1000 mb pressure level as input to the model. The computed results are in general consistent with observed patterns. In particular, it is shown that the positions of the meandering axis of the Kuroshio in summer and winter are markedly different. This work was supported by the Hong Kong Polytechnic University Research Grant No. 340/854.  相似文献   

趋势面分析中曲面拟合的优化     

郭洁冰 《地球科学与环境学报》1992,(4)

曲面拟合在数学地质中应用广泛。本文讨论用多项式函数对离散点观测值进行曲面拟合的优化过程。采用Gram—Schmidt正交化方法计算实矩阵的Moore-penrose型广义逆矩阵;并给出方程组的最短最小二乘解。优化后的曲面拟合方法降低了中间计算结果中坐标值的方次,因而计算出高阶趋势面系数时精度较高,也可以得到较高的多项式趋势面方程。  相似文献   

A 3-DIMENSIONAL BAROCLINIC CIRCULATION MODEL OF THE TROPICAL AND NORTHERN PACIFIC     

蔡怡  李毓湘 《中国海洋湖沼学报》1997,(1)

ImODUcrIONTheoceanisanimPoftantcomPonentofourenvironment,affchthedimatethroughairseaintCraCtions,anexamPleofwhichistheanomalousworkldirnatecausedbytheElNffoduetoanomaloustemPeratuasofthePadricthen,offersincmising1ydriportantresounatornankind,butbeauseofthescardtyoffiekldata,ourknowledgeofthedynandesofthevariousproanesthatoccurintheocean(eSpedallyinthedeepsea)isstilifarfromcomplete.WiththerapiddeveopmentofhighspedcomPutersandnumericalmathematics,numericalsimulationsarenowwidelyusedtocomP…  相似文献