Stability Analysis Of The Moving Interface In Piston- And Non-Piston-Like Displacements

From the macroscopic point of view, expressions involving reservoir and operational parameters are established for investigating the stability of moving interface in piston- and non-piston-like displacements. In the case of axi-symmetrical piston-like displacement, the stability is related to the moving interface position and water to oil mobility ratio. The capillary effect on the stability of moving interface depends on whether or not the moving interface is already stable and correlates with the wettability of the reservoir rock. In the case of non-piston-like displacement, the stability of the front is governed by both the relative permeability and the mobility ratio.

Growth Mechanism And Corrosion Behavior Of Ceramic Coatings On Aluminum Produced By Autocontrol Ac Pulse Peo

Ceramic coatings are produced on aluminum alloy by autocontrol AC pulse Plasma Electrolytic Oxidation (PEO) with stabilized average current. Transient signal gathering system is used to study the current, voltage, and the transient wave during the PEO process. SEM, OM, XRD and EDS are used to study the coatings evolution of morphologies, composition and structure. TEM is used to study the micro profile of the outer looser layer and inner compact layer. Polarization test is used to study the corrosion property of PEO coatings in NaCl solution. According to the test results, AC pulse PEO process can be divided into four stages with different aspects of discharge phenomena, voltage and current. The growth mechanism of AC PEO coating is characterized as anodic reaction and discharge sintering effect. PEO coating can increase the corrosion resistance of aluminum alloy by one order or two; however, too long process time is not necessarily needed to increase the corrosion resistance. In condition of this paper, PEO coating at 60 min is the most protective coating for aluminum alloy substrate. (C) 2008 Elsevier B.V. All fights reserved.

The Newest Developments Of Load-Unload Response Ratio (Lurr)

The Load Unload Response Ratio (LURR) method is an intermediate-term earthquake prediction approach that has shown considerable promise. It is inspiring that its predictions using LURR have been improving. Since 2004 we have made a major breakthrough in intermediate-term earthquake forecasting of the strong earthquakes on the Chinese mainland using LURR and successfully predicted the Pakistan earthquake with magnitude M 7.6 on October 8, 2005. The causes for improving the prediction in terms of LURR have been discussed in the present paper.

Sensitivity Analysis Of The Dimensionless Parameters In Scaling A Polymer Flooding Reservoir

A set of scaling criteria of a polymer flooding reservoir is derived from the governing equations, which involve gravity and capillary force, compressibility of water, oil, and rock, non-Newtonian behavior of the polymer solution, absorption, dispersion, and diffusion, etc. A numerical approach to quantify the dominance degree of each dimensionless parameter is proposed. With this approach, the sensitivity factor of each dimensionless parameter is evaluated. The results show that in polymer flooding, the order of the sensitivity factor ranges from 10(-5) to 10(0) and the dominant dimensionless parameters are generally the ratio of the oil permeability under the condition of the irreducible water saturation to water permeability under the condition of residual oil saturation, density, and viscosity ratios between water and oil, the reduced initial oleic phase saturation and the shear rate exponent of the polymer solution. It is also revealed that the dominant dimensionless parameters may be different from case to case. The effect of some physical variables, such as oil viscosity, injection rate, and permeability, on the dominance degree of the dimensionless parameters is analyzed and the dominant ones are determined for different cases.

Relationship between strain localization and catastrophic rupture

In order to explore a prior warning to catastrophic rupture of heterogeneous media, like rocks, the present study investigates the relationship between surface strain localization and catastrophic rupture. Instrumented observations on the evolution of surface strain field and the catastrophic rupture of a rock under uniaxial compression were carried out. It is found that the evolution of surface strain field displays two phases: at the early stage, the strain field keeps nearly uniform with weak fluctuations increasing slowly; but at the stage prior to catastrophic rupture, a certain accelerating localization develops and a localized zone emerges. Based on the measurements, an analysis was performed with local mean-field approximation. More importantly, it is found that the scale of localized zone is closely related to the catastrophic rupture strain and the rupture strain can be calculated in accord with the local-mean-field model satisfactorily. This provides a possible clue to the forecast of catastrophic rupture. (c) 2007 Elsevier Ltd. All rights reserved.

Study on flow characteristics of solid/liquid system in lysozyme crystal growth

During the process of lysozyme protein crystallization with batch method, the macroscopic flow field of solid/liquid system was observed by particle image velocimetry (PIV). Furthermore, a normal growth rate of (110) face and local flow field around a single protein crystal were obtained by a long work distance microscope. The experimental results showed that the average velocity, the maximal velocity of macroscopic solid/liquid system and the velocity of local flow field around single protein crystal were fluctuant. The effective boundary layer thickness delta(eff), the concentration at the interface Q and the characteristic velocity V were calculated using a convection-diffusion model. The results showed that the growth of lysozyme crystal in this experiment was dominated by interfacial kinetics rather than bulk transport, and the function of buoyancy-driven flow in bulk transport was small, however, the effect of bulk transport in crystal growth had a tendency to increase with the increase of lysozyme concentration. The calculated results, also showed that the order of magnitude of shear force was about 10(-21) N, which was much less than the bond force between the lysozyme molecules. Therefore the shear force induced by buoyancy-driven flows cannot remove the protein molecules from the interface of crystal.

Numerical-simulation of ac plasma-arc thermodynamics

A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequency range of 10-10(2) Hz which includes most industry ac arc frequencies. (C) 1994 Academic Press, Inc.

A solution to the upward migration of an intrusion

The evolution of the upward migration of the magma is a nonlinear and unstable problem in mathematics. It is difficult to solve it. And using the numerical method, the solution is relatively tedious and time-consuming. This paper introduces a method of the instantaneous point source to solve the linear and unstable heat conduction equation during the infinite period of time instead of the solution of the nonlinear and unstable heat conduction equation. The results obtained by this method coincide with those by the numerical method, meaning that this method offers a simple way to solve the nonlinear and unstable heat conduction equation.

The influence of microcrack density on the elastic and fracture mechanical properties of stripa granite

Microcracks can have a strong influence on the elastic and fracture mechanical properties of rocks if they are numerous, or if they are orientated in unfavourable directions in anisotropic rocks in particular. This paper presents results from a great number of mechanical tests on Stripa granite containing various amounts of microcracks. Variations in the microcrack density were obtained by shock-heating the rock at different temperatures in the range 100–600°C for 3 h.

The concentration-jump coefficient in a rarefied binary gas-mixture

The results presented are obtained from sound velocity measurements, uniaxial compression tests, Brazilian tests and three-point bending tests. The density of microcracks in the heated rock is studied by means of optical microscopy, SEM and differential strain analysis (DSA).

激波作用下岩石损伤试验及评价方法

通过水中爆炸激波对试样的损伤试验来模拟激波对地层岩石的破坏作用。试验中观测了爆炸后试样内部裂纹形貌的分布，利用自制传感器测到了试样内部的激波压力，优化筛选出了损伤度模型。通过对试样弹性波速进行处理和分析，给出了试样的动态损伤阈值求解方法。结果表明，激波在试样中的传播符合指数衰减规律，相对损伤度、无量纲波速的平方、无量纲拉应力它们两两之间呈线性关系。

驱油体系的驱油效率及其在模拟岩芯表面的润湿性研究

为了研究驱油体系在模拟岩芯表面的润湿性，为微重力应用研究提供依据，选择胜利纯梁采油厂c6—41井原油，应用正交实验设计，通过最低瞬时界面张力测定，筛选出阴离子表面活性剂sDc—V、非离子表面活性剂FBB、HPAM和复碱的驱油体系配方．开展室内模拟驱油实验，同时测定驱油体系溶液对模拟岩芯的接触角，并且关联驱油效率和接触角之间的关系，发现驱油效率越高，接触角值越小．

溶菌酶晶体生长过程中固/液流动体系的流体特性

在用批量法生长溶菌酶晶体的过程中,使用粒子图像测速技术观测晶体生长固/液体系的宏观速度场,使用长工作距离显微镜测定了晶体(110)面的法向生长速率和晶体周围溶液的局域速度场.实验结果表明,固/液体系的平均流速、最大流速以及单个晶体周围的局域流速均具有起伏特性.基于蛋白质晶体的对流-扩散模型,计算了有效浓度边界层厚度δeff,界面溶质浓度Ci以及特征速度V.计算结果表明,在实验条件下,溶菌酶的晶体生长过程主要由表面动力学控制,浮力对流在质量输运中的份量很小,但随着过饱和度的增加,质量传输的份额有增大趋势.计算结果还表明,浮力对流所产生的剪切力的量级为10?21N,远小于溶菌酶分子间的键力,因此浮力对流产生的剪切力不会对溶菌酶晶体生长产生很大影响.

岩石爆炸增渗模型实验及DEM数值模拟研究

岩体中爆炸提高矿石的渗透性可以极大地提高采矿效率，是碎裂岩型矿床预裂浸出法的关键技术。混凝土与岩体都具有脆性材料的特性，因此用浇筑于铁桶中的混凝土试件进行模型实验研究岩体的爆炸增渗效果。铁桶可以提高实验效率，使边界条件更为简单和易于操作，但是，实验和原型的差异需要论证。用自主开发的基于连续介质力学模型的离散元方法，模拟了有铁桶边界的模型实验，验证了数值模拟方法的可行性及有效性，给出了有弹性侧限边界约束的混凝土和较大尺度无反射边界条件的岩石中的爆炸差别。在此基础上，分析了岩石中爆炸造成的岩石破坏规律。计算结果表明：岩石破坏面总面积和破坏区的最大裂缝宽度受药量和岩石的抗拉强度影响，破坏面总面积和裂缝宽度随药量增加而增大，随抗拉强度增大而减小；在药量相同的条件下，实际岩石环境下的岩块破坏程度比铁桶约束的大。模型实验和数值模拟相结合的办法可以对混凝土和岩石的爆炸破坏给出较为合理的结果。

有限长岩柱中纵波传播规律的离散元数值分析

以节理岩体等效刚度的概念为基础，讨论了离散元刚性块体模型中节理刚度的选取问题。采用面-面接触模型模拟了纵波在一维岩体中的传播，给出了纵波波形；研究了阻尼比、软弱夹层以及节理间是否可拉对波传播规律的影响。