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Open-File Report 2014–1109

Groundwater Resources Program

Prepared in cooperation with George Mason University

GRIDGEN Version 1.0: A Computer Program for Generating Unstructured Finite-Volume Grids

By Jyh-Ming Lien, Guilin Liu, and Christian D. Langevin

Thumbnail of and link to report PDF (1.93 MB)Abstract

GRIDGEN is a computer program for creating layered quadtree grids for use with numerical models, such as the MODFLOW–USG program for simulation of groundwater flow. The program begins by reading a three-dimensional base grid, which can have variable row and column widths and spatially variable cell top and bottom elevations. From this base grid, GRIDGEN will continuously divide into four any cell intersecting user-provided refinement features (points, lines, and polygons) until the desired level of refinement is reached. GRIDGEN will then smooth, or balance, the grid so that no two adjacent cells, including overlying and underlying cells, differ by more than a user-specified level tolerance. Once these gridding processes are completed, GRIDGEN saves a tree structure file so that the layered quadtree grid can be quickly reconstructed as needed. Once a tree structure file has been created, GRIDGEN can then be used to (1) export the layered quadtree grid as a shapefile, (2) export grid connectivity and cell information as ASCII text files for use with MODFLOW–USG or other numerical models, and (3) intersect the grid with shapefiles of points, lines, or polygons, and save intersection output as ASCII text files and shapefiles. The GRIDGEN program is demonstrated by creating a layered quadtree grid for the Biscayne aquifer in Miami-Dade County, Florida, using hydrologic features to control where refinement is added.

First posted February 25, 2015

For additional information, contact:
Office of Groundwater
U.S.Geological Survey
411 National Center
12201 Sunrise Valley Drive
Reston, VA 20192
http://water.usgs.gov/ogw/contact.html

GRIDGEN Software - http://water.usgs.gov/ogw/gridgen/

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Suggested citation:

Lien, Jyh-Ming, Liu, Guilin, and Langevin, C.D., 2015, GRIDGEN version 1.0—A computer program for generating unstructured finite-volume grids: U.S. Geological Survey Open-File Report 2014–1109, 26 p., https://dx.doi.org/10.3133/ofr20141109.

ISSN 2331-1258 (online)



Contents

Abstract

Introduction

Overview of the GRIDGEN Program

GRIDGEN Definition Blocks

Example

Summary and Conclusions

References Cited


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