AMESH A mesh creating program for the integral finite differencemethod: A User's Manual

摘要

Amesh program generates discrete grids for numerical modeling of flow and transport problems in which the formulation is based on integral finite difference method (IFDM). For example, the output of Amesh can be used directly as (part of) the input to TOUGH2 or TOUGH numerical Simulator (Pruess, 1987, 1990, Pruess, et al., 1996). The code Amesh can generate 1D, 2D or 3D numerical grids for a given set of locations, i.e. the centers of each discrete sub-domain. In the 2D aerial plane the Voronoi tessellation method is used (Voronoi, 1908; Ahuja, 1982; Aurehammer, 1991; Fortune, 1987, 1988, 1993). In this method we can create a mesh of elements, within model domain, where the interfaces between neighbor elements are the perpendicular bisectors of the line connecting the element centers. The interface distances are simply the medians of the line connecting the centers. To create the 3D grid, the vertical direction interface areas are always treated as horizontal projections of the 2D areal plane. In the lateral direction the interface areas are always vertical projections. In both cases the direction of gravity vector is given by the cosine of angle formed by the line joining the element centers and the vertical. From the list of element locations (center points), the program determines element volumes, and the connection information, i.e. areas, connection distances and the angle. The default input file is ''in''. The output files are ''eleme'' are ''conne'' and ''segmt''. The files ''eleme'' and ''come'' contain all the data required to describe a TOUGH2 input and together they describe the input TOUGH2 input file called ''MESH'', for the specified domain. The file ''segmt'' can be used to plot the geometrical shape of each element in each layer of the input domain. The input data into Amesh does not have to be ordered. AMESH uses a fast quaternary sorting algorithm (Fortune, 1988; Watson 1985) to sort and compute the adjacency relationships between nodes in the 2D plane.