MODFLOW-USG is a new version of the MODFLOW groundwater flow simulation code developed by the United States Geological Survey (USGS) which uses unstructured grids instead of rectilinear grids to discretize the model domain.
An unstructured grid is made up of triangular, rectangular or other polygon shaped geometries individually or in combination to discretize the groundwater model domain. This is in contrast to MODFLOW-2005 which uses structured, rectilinear grids. Unstructured grids require the use of the finite volume method whereas traditional structured grids are used with the finite difference method. [...]
Although MODFLOW-USG can be used with any grid geometry – triangles, rectangles, polygons – Visual MODFLOW Flex supports polygonal unstructured grids made up of Voronoi Cells.
Voronoi Cells make up all unstructured grids in Visual MODFLOW Flex. Voronoi Cells are a special type of polygon that honors the Control Volume Finite Difference (CVFD) constraints required by MODFLOW-USG. Using this grid geometry with MODFLOW-USG results in an efficient and robust numerical grid that can handle complex hydrogeological geometries and boundaries with ease – [...]
Ghost Node Correction is a technique that is applied to some unstructured grid types, e.g., Nested or Quad-tree Grids, whose geometries do not inherently satisfy the requirements of MODFLOW-USG. Because Voronoi Grids by definition satisfy the constraints, ghost node correction is not required. One of the geometric constraints for a Finite Volume grid is that the [...]
Increased Simulation Accuracy Unstructured grids permit local grid refinement along model features such as wells and boundary conditions, in addition to supporting fully discontinuous layers, both of which deliver high resolution detail and accuracy around areas that matter the most. Reduced Simulation Runtimes Traditional MODFLOW grid refinement often results in an excessive number of grid cells [...]
MODFLOW-USG can be used to simulate groundwater flow for virtually any application. However, It’s ability to handle complex geology makes it’s ideal for applications in mining where steep slope geology is often encountered. Flexible grid refinement capabilities make it suitable for large regional and watershed scale models.
The following processes and packages are supported: BAS, DIS, BCF, LPF, HFB CHD, FHB WEL, DRN, GHB, RIV STR, SFR, LAK, GAG SUB New Packages: DISU, CLN, GNC, SMS
Yes. If you currently use Visual MODFLOW Flex, you will already have a 3D conceptual model that defines the geologic layers, properties and boundary conditions independent of the grid. To run your model with MODFLOW-USG, simply auto-generate the unstructured grid and then run the simulation. Visual MODFLOW Flex’s multi-model environment allows you to manage both your [...]