水位下降条件下西安D7裂缝土体孔隙变化特征试验

为研究压缩性土体在孔隙水压力下降下所引起的孔隙变化特征,选取孔隙度及分形维数作为评判指标,以西安D7地裂缝两侧可压缩性土层为研究对象,借助三维CT扫描成像技术,依托Matlab计算平台及VG Studio Max图像处理软件,对在水位下降过程中可压缩性土体压缩变形引起的孔隙度和分形维数孔隙变化进行定量评价,并探讨了固结压缩过程中土体孔隙分形维数的变化规律及其影响因素。研究表明:孔隙度随压缩进行大幅降低,由压缩前4.36%降至0.61%;土体分形维数与孔隙度、上覆压力均呈线性相关性,相关系数分别为0.947 2和0.966 0;而且分形维数可以很好的表征孔隙分布特点,是孔隙度的有效补充;通过分析土样孔隙度与分形维数关系,为后期建立区域上地裂缝—地下水开采耦合模型提供参数赋值基础。

Study on Permeability of 2.5D Woven Reinforcement Materials with Fractal Theory

Permeability is one of the key issues in the design of molds and in the molding process for composite manufacture. As a disordered fibrous assembly, 2.5- dimension （2.5 D） woven reinforcement materials have complex structure. It poses a challenge to the study of pore structure and the establishment of the theoretical permeability model. Toward addressing this problem, a powerful tool called fractal theory emerged. According to the analysis of 2.5 D woven reinforcement material stmcture using fractal theory, it is found that the structure has an obvious fractal character. Therefore, a permeability fractal model of 2.5D woven reinforcement material was established by cormbining the Hagen-Poiseulle equation with Darcy law according to the capillary vessel fractal model in this paper. The permeability was expressed as a function of the fractal dimension and microstructure parameter of the porous media in this model. The theoretical model is verified by experimental tests and the measurement data are in good agreement with the results obtained from the fractal medel .

多孔LiOH孔隙特征及CO_(2)流动特性数值模拟

为了研究二氧化碳在新型多孔LiOH吸附剂孔隙中的流动规律,基于Sierpinski-Menger海绵结构建立三维分形孔隙模型,利用Fluent软件对LiOH孔隙中的气体流动进行数值模拟,分析不同流动速度(1、0.1、0.01 mm/s)下的流动规律。模拟结果表明,气体在海绵结构中流动具有分形特性,CO_(2)速率与动压在不同级数模型中分布一致,具有明显的对称性与相似性,说明在分形维数相同的情况下,不同级数模型具有相同的分形特征。通过对比3种入口气体流速(1、0.1、0.01 mm/s)对二氧化碳体积分数分布的影响,可知入口气体流速的增加有利于二氧化碳分布均匀,在允许的范围内增加入口气体流速有利于二氧化碳的吸附,提高LiOH吸附剂的吸附率。入口气体流速的改变只能改变CO_(2)动压、CO_(2)速率、总压的值,不影响它们在流场内的分布。这是由Sierpinski-Menger海绵分形模型自身的分形特性决定,不受边界条件的影响。可以得出总压力降与入口气体流速成线性关系。