In this paper, an unstructured grid generation algorithm is presented to produce two-and three-dimensional grids in porous media with networks of discrete fractures. The proposed grid generation algorithm considers underground contours map data to adapt unstructured grids to geological geometries. This allows construction of more realistic geometrical models. Sample two-and three-dimensional unstructured grids have been generated in complex porous media with seven intersecting fractures. Two-dimensional grids were generated within 0.17-2.37 s of CPU time. Generation of three-dimensional grids including grid quality improvement measures took 109 s of CPU time. This final grid contains 763 fracture cells and 49,403 matrix cells. Angle distribution histograms of the three-dimensional grids show no skewed and flat angles within fracture and matrix cells. Two-and three-dimensional computational unstructured grids have been generated for geometries similar to published fractured porous media test cases. Incompressible and immiscible water-oil flow simulations were then obtained using these computational grids. Simulations gave identical results with published data which confirms the computational feature of the proposed unstructured grid generation algorithm.
Most three dimensional tetrahedral grid generators can refine an initial grid in matter of seconds. But making an initial tetrahedral grid for complex geometry can be a tedious and time consuming task. This paper describes a novel procedure for generation of starting tetrahedral cells using hexahedral block topology. Hexahedral blocks are arranged around an aerodynamic body to fill-up a computational flow domain. Each of the hexahedral blocks is then decomposed into six tetrahedral elements to obtain an initial tetrahedral grid around the same aerodynamic body. This resulted in an algorithm that enables users to produce starting tetrahedral grids for variety of aerodynamic configurations. To construct an initial starting tetrahedral grid suitable for computational flow simulations, representing a solid surface geometry (fuselage or a wing section) attached to a plane-of-symmetry, a topology containing at least 5 hexahedral blocks is required. This results in an initial starting grid consisting of 30 tetrahedral cells with 74 faces and 16 vertices, which is the same number of vertices as for the hexahedral blocks. Since the number of vertices and their coordinate locations are kept the same, a connectivity matrix can be produced to describe the forming faces of the tetrahedral grid. This procedure was performed for a single block, 5-block, and 9-block topologies to produce starting tetrahedral cells for numerous domain size and shapes.
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