Applications of quadrilateral and quadrilateral-prism mesh generation in overland and subsurface simulations

Abstract

This paper developed an automatic mesh generator used for simulating real-world problems of hydrological cycles, fluid flow, salinity and thermal transport, sediment and water quality transport, etc. The 2-D overland area was discretized with quadrilaterals based on conformal mapping technique. A position-percent interpolation equation was established to determine nodal vertical-coordinates and match boundaries. For 3-D simulations of subsurface zones, an additional mesh generation method was proposed to create quadrilaterals for filling the empty regions along river reaches and around junctions with storage, ponds or lakes. In order to deal with special storage region with an odd number of boundary nodes, an additional triangle was inserted. Five topological optimization templates were proposed to improve the quality of degenerated elements. This paper proposed the basic algorithms to generate quadrilateral-prism meshes through stretching the quadrilateral mesh along vertical directions based on material domains. Aiming at four types of fractures, corresponding extraction methods were presented to preserve geometric features. In order to accommodate the need for overland and subsurface simulations, 1-D/2-D/3-D correspondence was established between rivers, junctions, ponds, lakes, control structures and finite element meshes. Finally, several realistic hydrologic and geologic examples for meshing multi-domain areas were provided to demonstrate the accuracy and effectiveness of the mesh generator developed in this paper.