Steady flows driven by sources of random strength in heterogeneous aquifers with application to partially penetrating wells     

Gerardo Severino  Alessandro Santini  Angelo Sommella 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(4):567-582

Average steady source flow in heterogeneous porous formations is modelled by regarding the hydraulic conductivity K(x) as a stationary random space function (RSF). As a consequence, the flow variables become RSFs as well, and we are interested into calculating their moments. This problem has been intensively studied in the case of a Neumann type boundary condition at the source. However, there are many applications (such as well-type flows) for which the required boundary condition is that of Dirichlet. In order to fulfill such a requirement the strength of the source must be proportional to K(x), and therefore the source itself results a RSF. To solve flows driven by sources whose strength is spatially variable, we have used a perturbation procedure similar to that developed by Indelman and Abramovich (Water Resour Res 30:3385–3393, 1994) to analyze flows generated by sources of deterministic strength. Due to the linearity of the mathematical problem, we have focused on the explicit derivation of the mean head distribution G _d (x) generated by a unit pulse. Such a distribution represents the fundamental solution to the average flow equations, and it is termed as mean Green function. The function G _d (x) is derived here at the second order of approximation in the variance σ² of the fluctuation (where K _A is the mean value of K(x)), for arbitrary correlation function ρ(x), and any dimensionality d of the flow domain. We represent G _d (x) as product between the homogeneous Green function G _d ⁽⁰⁾(x) valid in a domain with constant K _A , and a distortion term Ψ _d (x) = 1 + σ²ψ _d (x) which modifies G _d ⁽⁰⁾(x) to account for the medium heterogeneity. In the case of isotropic formations ψ _d (x) is expressed via one quadrature. This quadrature can be analytically calculated after adopting specific (e.g.. exponential and Gaussian) shape for ρ(x). These general results are subsequently used to investigate flow toward a partially-penetrating well in a semi-infinite domain. Indeed, we construct a σ²-order approximation to the mean as well as variance of the head by replacing the well with a singular segment. It is shown how the well-length combined with the medium heterogeneity affects the head distribution. We have introduced the concept of equivalent conductivity K ^eq(r,z). The main result is the relationship where the characteristic function ψ^(w)(r,z) adjusts the homogeneous conductivity K _A to account for the impact of the heterogeneity. In this way, a procedure can be developed to identify the aquifer hydraulic properties by means of field-scale head measurements. Finally, in the case of a fully penetrating well we have expressed the equivalent conductivity in analytical form, and we have shown that (being the effective conductivity for mean uniform flow), in agreement with the numerical simulations of Firmani et al. (Water Resour Res 42:W03422, 2006).  相似文献   

气象参数对人体舒适度的影响研究   总被引：2，自引：0，他引：2  

郑有飞  余永江  谈建国  吴荣军  许遐祯 《气象科技》2007,35(6):827-831

为研究气象参数对人体舒适度的影响,用慕尼黑人体热量平衡模型(MEMI)分析了南京舒适感的概率分布、年际、月际变化以及气象参数和生理等效温度(PET)的相互关系。结果表明:各舒适感觉出现的频率差别较大,在年际分布上有波动,月际分布上很不均匀。PET随温度线性增加,在多云天气1m/s风速时增幅最大;PET和平均辐射温度之间也是线性增加关系,温度较高时增幅大;PET随着风速的增加呈现先快后慢的非线性减小关系,低温时降幅明显,高温阴天时降幅最小;相对湿度在高温时可使PET显著增加。  相似文献   

Simplified equivalent multiple baseline solutions with elevation-dependent weights     

Yunzhong Shen  Bofeng Li  Guochang Xu 《GPS Solutions》2009,13(3):165-171

Since the assumption of all stations tracking the same satellites with identical weights was previously employed by Shen and Xu (GPS Solut 12:99–108, 2008) to derive the simplified GNSS single- and double-differenced equivalent equations, this supplementary paper expands these simplified equations in the case of each station tracking different satellites with elevation-dependent weights. Numerical experiments are performed to demonstrate the computational efficiency of the simplified equivalent algorithm relative to the traditional method in various scenarios of multi-baseline solutions with tracking different satellites. The fast computational speed of the simplified equivalent algorithm will potentially benefit the local, regional and even global GNSS multi-baseline solutions as well as the combined GNSS application.

Guochang XuEmail:

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秋季低纬太平洋海温异常激发的准PNA型     

方之芳  贺艳 《成都信息工程学院学报》1991,(Z1)

本文应用统计方法讨论6～11月的准PNA型,得到如下结论: 秋季,低纬中太平洋热源异常,能发出位置与PNA型相类似的遥相关型——准PNA型。这种遥相关型呈二维Rossby波列,具有相当正压结构,在西风带中沿固定波导向极向东传播,从而影响中太平洋和北美天气。 夏季,由于热源位置的差异,则不存在与PNA型相类似的遥相关型。从而认为热源的扰动在遥相关型的成因上起着举足轻重的作用。  相似文献   

重磁力联合反演在研究复杂盆地基底构造中的应用     

王西文 《地球科学与环境学报》1993,(1)

本文采用重磁力联合反演方法,计算了民和盆地基底深度和视磁化强度。针对该盆地特点,设计了等效和非均质重力反演模型,在约束条件下分块反演得到准确可靠的基底深度;用基底深度和航磁异常反演基底视磁化强度,根据岩石磁化率参数,判定基底岩性横向分布。该方法不仅能提供盆地基底构造形态,而且能提供基底岩性信息。  相似文献   

Convergence-control approach for rock tunnels reinforced by grouted bolts,using the homogenization concept     

Reza R. Osgoui  Pierpaolo Oreste 《Geotechnical and Geological Engineering》2007,25(4):431-440

The scope of this paper is to introduce a method for the analysis of rock tunnels reinforced by grouted bolts, based on the convergence-control approach. The analytical formulations presented in this paper refers to an elasto-plastic behavior of the rock mass and the latest Hoek and Brown yield criterion (Version 2002). In order to model the reinforced plastic zone, the equivalent material approach was taken into account such that the apparent strength of the rock mass is improved as a consequence of the bolting effect. The general design guides and examples presented are intended to facilitate the comprehension and application of the proposed analytical solution in practice.  相似文献   

Comment on the effect of anisotropy on the onset of convection in a porous medium     

D.A. Nield 《Advances in water resources》2007

The effect of anisotropy on the onset of convection in a saturated porous medium is discussed. In particular, the case of time-dependent density-driven convection is examined. The applicability of the value of an equivalent Rayleigh number as the criterion for the onset of convection is discussed.  相似文献   

Inverse analysis of weak and strong motion downhole array data from the M_w7.0 Sanriku-Minami earthquake     

D. Assimaki  J. Steidl 《Soil Dynamics and Earthquake Engineering》2007,27(1):73-92

A hybrid optimization scheme, comprising a genetic algorithm in series with a local least-squares fit operator, is used for the inversion of weak and strong motion downhole array data obtained by the Kik-Net Strong Motion Network during the M_w7.0 Sanriku-Minami Earthquake. Inversion of low-amplitude waveforms is first employed for the estimation of low-strain dynamic soil properties at five stations. Successively, the frequency-dependent equivalent linear algorithm is used to predict the mainshock site response at these stations, by subjecting the best-fit elastic profiles to the downhole-recorded strong motion. Finally, inversion of the mainshock empirical site response is employed to extract the equivalent linear dynamic soil properties at the same locations. The inversion algorithm is shown to provide robust estimates of the linear and equivalent linear impedance profiles, while the attenuation structures are strongly affected by scattering effects in the near-surficial heterogeneous layers. The forward and inversely estimated equivalent linear shear wave velocity structures are found to be in very good agreement, illustrating that inversion of strong motion site response data may be used for the approximate assessment of nonlinear effects experienced by soil formations during strong motion events.  相似文献   

饱和湿大气Brunt-V3/4is3/4l3/4频率及修正的相当位温   总被引：1，自引：0，他引：1       下载免费PDF全文

刘栋  高守亭 《气象学报》2003,61(3):379-383

实际大气中受扰动的饱和气块发生凝结后 ,凝结水会部分脱离气块。以前研究饱和湿大气的Brunt V is l 频率 (N2 m)没有考虑凝结水的部分脱离 ,相当位温 (θe)也忽略了饱和气块的混合比的作用。文中针对这些不足 ,在假设饱和空气中只存在气液转换条件下 ,推导出液态水部分脱离气块的、更符合实际情况的N2 m 表达式和修正的饱和湿大气θe 表达式。新的N2 m 表达式增加了部分脱离气块的液态水的作用项 ,新的θe 表达式中包含有饱和气块的混合比 ,并对有关的表达式分别作了讨论和比较  相似文献   

碳酸盐岩喀斯特溶洞和裂缝系统的地震模拟与预测   总被引：10，自引：0，他引：10  

贺振华  杜正聪  文晓涛 《地球科学进展》2004,19(3):399-402

提出了有助于确定碳酸盐岩裂缝带和喀斯特溶洞系统空间分布的地震正演模拟和预测方法。地震正演方法包含两个关键步骤，一是利用弹性波动方程计算含缝洞介质的有效弹性参数，另一步骤是根据有效弹性参数构成的等效地质模型，用单程声学波动方程进行波场延拓。数值模拟和实际地震数据的例子说明，将地震正演剖面与地震偏移剖面相结合进行对比分析有可能识别和预测碳酸盐岩地层中的缝洞发育带。  相似文献