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DIRECT GENERATION OF FINITE ELEMENT MESHES OF COMPOSITE MICRO AND MESOSTRUCTURE FROM 3 D IMAGING : APPLICATION TO FLOW COMPUTATION

Introduction In recent years, imaging techniques, like X-ray tomography, have been used to obtain precise geometrical and topological information. For scientific computation, accuracy of numerical representations may play a key role: image acquisition and its efficient transposition on a numerical sample have shown to be of prime importance. The passage from the image to a finite element mesh allows on one hand, the construction of a numerical representation but, on the other hand, may also reduce the size of the stored data. The first step (before building a mesh) is usually to perform the image segmentation, that is, to partition the image into its multiple objects, so that it becomes easier to analyse it [1]. The result of this segmentation can be regions of the image where the pixels are similar with respect to a characteristic or property (like, for example, the colour), or extracted contours. Secondly, a mesh is built from the segmented image until the optimal mesh is obtained, by using different techniques. One class of segmentation techniques is based on an implicit description of the phases, through level set functions [2-3]. In this paper, we propose to simultaneously segment the image and produce an adapted mesh adequate to perform numerical simulations using the image data, based on the reinitialization of an implicit function coupled to an anisotropic mesh adaptation technique [4]. Simulations performed concern mainly multiphase flow and, in particular, flows through solid fibrous media.