Accuracy of the Renormalization Method for Computing Effective Conductivities of Heterogeneous Media

The accuracy of the renormalization method for upscaling two-dimensional hydraulic conductivity fields is investigated, using two canonical 2 × 2 blocks: a checkerboard geometry and a geometry in which three of the cells have conductivity K ₁ and the other has conductivity K ₂. The predictions of the renormalization algorithm are compared to the arithmetic, harmonic and geometric means, as well as to theoretical predictions and finite element calculations. For the latter geometry renormalization works well over the entire range of the conductivity ratio K ₂/K ₁, but for the checkerboard geometry the error becomes unbounded as the conductivity ratio grows.     

井下光纤微地震监测系统设计及应用

为满足油气开发中微地震监测的需求,基于时分复用方案设计了一种新型井下3分量光纤微地震监测系统.结合室内测试,该系统本底噪声小于?101 dB,动态范围大于120 dB,级间串扰小于?67 dB,满足微地震信号探测的需求.该系统已成功应用于新疆油田水力压裂微地震现场探测.监测结果表明:该系统可清晰捕捉微地震的P波、S波信...     

水轮机转轮内部磨损预测

本文利用ｋ－ε－Ａｐ两相湍流模型计算水轮机转轮中泥沙固液两相湍流。根据液相和固相三维流速场的计算结果数值预估转轮叶片面的泥沙磨损。     

深层地下地应力测量

介绍了对某水力压裂法处置中放废液工程进行的深层地下地应力测量的有关情况。利用压阻型压力传感器和压力盒相结合的办法克服压力探头敏感面小带来的测量困难 ,成功进行了地下数百米深度处地应力测量。实际测量表明系统工作可靠 ,测量数据可信。     

水力机械转轮内的CFD分析及优化设计

本文基于Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程和标准的ｋ－ε紊流模型,模拟了转轮内的三维紊流场。同时,建立了一种现代水力机械转轮的设计方法;采用ＣＡＤ－ＣＦＤ系统,依据三维紊流场的预测结 果优化转轮内相关的几何参数,使得转轮内的流态接近理想流态,从而保证优化转轮的良好性能。     

On the finite displacement problem of a hollow cylinder under internal and external pressures

Using the method of successive approximations we find of this boundary-value problem the first-and second-order solutions. And then we obtain the formulae in the second approximation for the displacement, strain, and stress fields. Also, our results show that after deformation (i) a cross-section of the cylinder must be displaced into a plane section perpendicular to the central axis of the cylinder; and (ii) neither the sum of the strain components E _RR ⁽²⁾ and E ⁽²⁾ nor the sum of the stress components E _RR ⁽¹⁾ and E ⁽¹⁾ maintains contant throughout the cylinder. The latter effect, which is absent from classical elasticity, bears respensibility for the presence of the E _ZZ ⁽¹⁾ . Moreover, there exhibits a linear relation between E _ZZ ⁽¹⁾ and (E _RR ⁽²⁾ +E _OO ⁽¹⁾ ), with the proportionality coefficients depending only on the material of the cylinder.     

On the global asymptotic stability of periodic solutions of a class of ecological system

In this paper, we have made reaearches on the mathematical models which have three populations of mutual action: We have obtained the sufficient conditions respectively for the systems(*)and(**)for existence and uniqueness of single positive periodic solutions which are globally asymptotically stable.     

Role of Na-Montmorillonite on Microbially Induced Calcium Carbonate Precipitation

The use of additives has generated significant attention due to their extensive application in the microbially induced calcium carbonate precipitation (MICP) process. This study aims to discuss the effects of Na-montmorillonite (Na-MMT) on CaCO₃ crystallization and sandy soil consolidation through the MICP process. Compared with the traditional MICP method, a larger amount of CaCO₃ precipitate was obtained. Moreover, the reaction of Ca²⁺ ions was accelerated, and bacteria were absorbed by a small amount of Na-MMT. Meanwhile, an increase in the total cementing solution (TCS) was not conducive to the previous reaction. This problem was solved by conducting the reaction with Na-MMT. The polymorphs and morphologies of the CaCO₃ precipitates were tested by using X-ray diffraction and scanning electron microscopy. Further, when Na-MMT was used, the morphology of CaCO₃ changed from an individual precipitate to agglomerations of the precipitate. Compared to the experiments without Na-MMT in the MICP process, the addition of Na-MMT significantly reduced the hydraulic conductivity (HC) of sandy soil consolidated.     

土壤侵蚀的流体力学机制（Ⅱ）－风蚀

土壤的加速侵蚀已成为当前全球性环境灾害之一．对土壤侵蚀及其预防、控制的研究引起了人们的普遍关注．本文通过对国外文献的广泛调研,系统地分析与评价了有关土壤风力侵蚀的研究进展．      

Flux‐corrected transport technique for open channel flow

In modeling flow in open channels, the traditional finite difference/finite volume schemes become inefficient and warrant special numerical treatment in the presence of shocks and discontinuities. The numerical oscillations that arise by making use of a second‐ and higher‐order schemes require some additional smoothing mechanism. A characteristic feature of high‐resolution schemes lies in smooth capturing of the shock fronts. This paper provides a general formulation for a flux‐corrected transport algorithm to the one‐dimensional open channel flow equations. The preliminary results presented show that the present algorithm is an efficient, conservative and robust tool that can be easily coded. To demonstrate the robustness of the present formulation, results are compared with other published numerical results, experimental data and analytical solutions when available. In particular, a comprehensive study on the effect of the source term, dry bed, variable width channel, steep sloping channel and flow with mixed flow conditions (as in a hydraulic jump) has been carried out to test the efficacy of the present algorithm. Copyright © 1999 John Wiley & Sons, Ltd.