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101.
A self-consistent scheme is used in order to determine the permeability of a cracked porous medium. For weak values of the permeability of the uncracked porous matrix, it is found that the order of magnitude of the permeability increases beyond a critical threshold of the crack density parameter. In the framework of a micromechanical model, it is shown that both the evolution of crack opening and the crack propagation are controlled by Terzaghi's effective stress which therefore captures the coupling between permeability and mechanical loading. To cite this article: L. Dormieux, D. Kondo, C. R. Mecanique 332 (2004). 相似文献
102.
P. Vainshtein M. Shapiro C. Gutfinger 《International Journal of Multiphase Flow》2002,28(12):1945-1963
Flow past and within an isolated permeable spheroid directed along its axis of symmetry is studied. The flow velocity field is solved using the Stokes creeping flow equations governing the fluid motion outside the spheroid, and the Darcy equation within the spheroid. Expressions for the hydrodynamic resistance experienced by oblate and prolate spheroids are derived and analyzed. The limiting cases of permeable circular disks and elongated rods are examined. It is shown that the spheroid’s resistance varies significantly with its aspect ratio and permeability, expressed via the Brinkman parameter. 相似文献
103.
We study the problem of flow permeability of fracture joints using Lattice-Gas Automata simulations. We model the fracture as a rough channel bounded by a self-affine surface. Changing the surface roughness exponent, rough walls having different microstructures are obtained. Different relative roughnesses — defined as the height of the largest surface asperity divided by the mean aperture — are obtained pulling apart the two surfaces that constitute the rough walls of the channel. We calculate the macroscopic variables volume flow rate and pressure difference using microscopic balances. In the low Reynolds number regime the pressure difference and the flow rate are linearly related (the behavior is described by Darcy's law). In this regime, we study the effect of geometry on the permeability. We have found that permeability is independent of the surface roughness exponentH and it is fully determined in terms of the relative roughness and mean aperture of the fracture joint. For larger Reynolds numbers a transition to a regime in which pressure difference and flow rate are not longer linearly related is observed. This transition is observed in a domain of Reynolds numbers for which the behavior in a smooth channel remains linear. We discuss this transition. 相似文献
104.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):1185-1197
The polymerization of 4,4-bis(t-butylbenzoylmethyl)-1,6-hepta-diyne (BTBH) was carried out by group 5,6-transition metal catalysts. MoCl5- as well as WCl6-based catalysts were effective for the cyclopolymerization of BTBH. The polymer structure was analyzed to have conjugated backbone and recurring 5-membered ring by various spectroscopes. The polymer showed good solubility in common organic solvents. The polymer had good thermal stability and mechanical property. The oxygen permeability coefficient (PO2) and permselectivity of oxygen to nitrogen (PO2/PN2) of poly(BTBH) with bulky and rigid t-butyl benzoyl group were 23.2 barrer and 4.63, respectively. 相似文献
105.
106.
R.K. Roy A.K. Panda M. Ghosh A. Mitra R.N. Ghosh 《Journal of magnetism and magnetic materials》2009,321(18):2865-2870
The 25 mm wide ribbons of Fe-6.5 wt% Si alloy have been developed by melt spinning technique, showing sufficient ductility and white silver appearance. Two magnetic transitions take place at 676 and 760 °C due to the formation of B2 ordered phase and A2 disordered paramagnetic phase, respectively. The saturation magnetization of the ribbon is 17.5 kG under the applied field of 12 kG. The as-cast ribbons consist of disordered A2 structure with a low volume of B2 phases while the annealed microstructure comprises a dispersion of B2 domains in the disordered A2 matrix. The alloy shows the enhancement of the soft magnetic properties with a reduction in coercivity from 150 A/m in the as-cast state to 45 A/m in the annealed condition at 850 °C. 相似文献
107.
A volume averaging approach is used to estimate the porous media permeability. Contrary to traditional methods that rely on solving the Navier-Stokes equations for laminar flow, this approach has the advantage that it does not require the specification of some physical conditions and parameters (pressure drop and viscosity). Numerical results on synthetic models of porous media showed that (i) the local porous medium configuration has an important effect on the permeability value, and (ii) the Carman-Kozeny equation cannot describe the permeability behavior as a function of porosity and characteristic lengths. In turn, our results indicate that simple empirical equations, commonly used in practice, are unable to describe the permeability functionalities over a broad range of porous media configurations. 相似文献
108.
电压依赖阴离子选择性通道(Voltage dependent anion-selective channel, VDAC)是线粒体外膜上重要的通道蛋白,转运线粒体和细胞质之间的代谢物,对于线粒体发挥生理功能具有决定性作用. 为研究VDAC分子的调控机制,在电场存在和不存在的情况下,我们对I型人类VDAC分子(hVDAC1)分别进行了分子模拟研究. 比较结果显示:外加电场的有无与方向变化对hVDAC1分子的运动模式和离子通过过程影响不明显,hVDAC1分子仍然保持以N端α螺旋在β桶内横向运动为主的运动模式. 综合模拟结果和相关的实验结果,我们推测,发表的hVDAC1晶体结构可能不是其发挥生理功能的结构状态. 相似文献
109.
V.A.F.Costa 《中国颗粒学报》2009,7(3)
This work reports on fluid flow in a fluid-saturated porous medium, accounting for the boundary and inertial effects in the momentum equation. The flow is simulated by Brinkman-Forchheimer-extended Darcy formulation (DFB), using MAC (Marker And Cell) and Chorin pressure iteration method. The method is validated by comparison with analytic results. The effect of Reynolds number, Darcy number, porosity and viscosity ratio on velocity is investigated. As a result, it is found that Darcy number has a decisive influence on pressure as well as velocity, and the effect of viscosity ratio on velocity is very strong given the Darcy number. Additional key findings include unreasonable choice of effective viscosity can involve loss of important physical information. 相似文献
110.