Streamline-oriented grid generation for transport modelling in two-dimensional domains including wells

Flownets are useful tools for the visualization of groundwater flow fields. Using orthogonal flownets as grids for transport modeling is an effective way to control numerical dispersion, especially transverse to the direction of flow. Therefore tools for automatic generation of flownets may be seen both as postprocessors for groundwater flow simulations and preprocessors f or contaminant transport models. Existing methods to generate streamline-or iented grids suffer from drawbacks such as the inability to include sources in the interior of the grid. In this paper, we introduce a new method for the generation of streamline-oriented grids which handles wells in the grid interior, and which produces orthogonal grids for anisotropic systems. Str eamlines are generated from an accurate velocity field obtained from the so lution of the mixed-hybrid finite element method for flow, while pseudopote ntials, which are orthogonal to the streamlines, are obtained by a standard finite element solution of the pseudopotential equation. A comprehensive m ethodology for the generation of orthogonal grids, including the location o f stagnation points and dividing streamlines, is introduced. The effectiven ess of the method is illustrated by means of examples. A related paper pres ents a compatible formulation of the solution for reactive transport, while a second related paper gives a detailed quantitative assessment of the var ious forms of modelled mixing and their effect on the accuracy of simulatio ns of the biodegradation of groundwater contaminants, (C) 1999 Elsevier Sci ence Ltd. All rights reserved.