Abstract:

Building a precise pore network by using 3D reconstruction lays the foundation for studying the fluid flow as well as heat and mass transfer in porous media, in which the medial axis extraction of pore structure is the key to reconstruction. Among the thinning algorithms to extract medial axis, simple points method has its advantages over accuracy and parallel operation, whereas its application to pore structure analysis is relatively few. Based on the fully parallel thinning algorithm of the simple points method, a medial axis extraction method specializing in porous media is developed, consisting of the following four major steps:image processing, reconstruction matrix generating, layer-by-layer marking and parallel thinning. Applying the proposed method to 230 objects with typically ordered pore structures and a reconstruction model of an activated carbon accumulation, the medial axes topologically equivalent to each object are obtained and the pore radiuses are calculated fast and precisely. By comparing the pore volume calculated from the media axis and its corresponding radius with actual pore volume, it is found that the relative error of the pore volume is lower than 6% eventually. The results show that the proposed method is capable of obtaining the medial axis preserving the geometry and connectivity commendably and resisting the influence of surface irregular variation effectively, hence can be used for nondestructive quantitative analysis and pore network extraction.

Key words: porous media, model, pore network, medial axis, algorithm

摘要：

应用三维重构技术建立介尺度下的多孔介质孔隙网络模型是分析多孔介质内流体流动与传热传质过程的基础，其中孔隙网络中轴的提取是三维重构的关键环节。在提取中轴的细化算法中，简单点集合细化方法具有准确、可并行的特点，但较少应用于多孔介质的结构分析。基于简单点集合细化方法中的完全并行细化算法，建立了一种面向多孔介质的孔隙网络中轴提取方法，包含图像处理、重构矩阵生成、逐层标记、并行细化四个主要步骤。以计算机生成的230个典型的有序多孔介质模型及1个活性炭堆积试样重构模型为研究对象，应用本方法获得了与研究对象的孔隙空间具有拓扑等价性的孔隙网络中轴，快速准确地计算了孔隙半径，利用中轴形态与孔隙半径计算孔隙占据的空间大小与实际体积比较，发现研究对象的孔隙体积计算值相对误差最终稳定在6%以下。结果表明，由本方法获得的中轴反映了孔隙空间的几何形状、减小了孔隙与固体界面处不规则变化的干扰，可用于多孔介质孔隙结构的无损定量分析及孔隙网络建模。

关键词: 多孔介质, 模型, 孔隙网络, 中轴, 算法