Visual MODFLOW Flex 2014.1 delivers support for MODFLOW-USG – a new finite volume version of the USGS MODFLOW groundwater modeling program, that uses flexible and efficient unstructured grid geometries.
Benefits of Unstructured Grids
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 outside the areas of interest which leads to an inefficient numerical model with unnecessary long run times. With unstructured grids, the grid refinement is focused only to the areas of interest, resulting in much fewer grid cells, more stable grid structures, and therefore reduced run times.
Further Reading: MODFLOW-USG Benchmark Tests Demonstrate a 96% Reduction in Simulation Run Times
Superior Modeling of Complex Geology
Unstructured grids are flexible and conform easily to the natural variability found in surface features and subsurface stratigraphy. Unstructured grid layers permit discontinuous layers that pinch-out to zero thickness, providing a more realistic representation of complex hydrogeological conditions, and improved model stability.
Increased Numerical Stability
Unstructured grids in Visual MODFLOW Flex 2014.1 are composed of a special type of polygon called Voronoi Cells. Voronoi Cells are superior to other unstructured grid geometries (nested grids, quad-tree grids) as they completely honor the Control Volume Finite Difference (CVFD) constraints, and therefore do not require the Ghost Node Correction (GNC) package. In addition, well and boundary condition nodes coincide exactly with the grid nodes. This results in an efficient, robust and dependable numerical grid, with improved convergence and accuracy.
Why use Visual MODFLOW Flex for MODFLOW-USG simulations?
Intuitive, Easy-to-use Interface
Visual MODFLOW Flex 2014.1 provides an easy-to-use interface for defining model inputs, running the model and visualizing impressive detailed 2D/3D renderings of model results.
A Multi-Model Environment
The conceptual modeling approach in Visual MODFLOW Flex allows you to easily generate an unlimited amount of numerical models from a single 3D conceptual model – all within a single project. Results from multiple numerical models can be compared and analyzed side-by-side within the same environment. This allows you to compare various MODFLOW-USG models with various levels of refinement, and validate against MODFLOW-2005 models.
The Conceptual Modeling Approach
The conceptual modeling approach makes it easy to build a 3D MODFLOW-USG numerical model. GIS-based representations of your boundary conditions (points, polygons, polylines) are automatically included in the grid generator, providing for a natural and intuitive workflow. Discontinous formations defined in the conceptual model are automatically converted to zero thickness layers in the unstructured grid. Numerical model inputs such as properties, wells, and boundaries are automatically populated from conceptual data.
Robust Grid Generator
Visual MODFLOW Flex has a built-in grid generator for unstructured grids that provides reasonable default settings for voronoi cells, and control over refinement levels around the model boundary, lines, and wells. Grids are efficiently refined around features, while maintaining the CVFD criteria, for superior performance and accuracy.
Powerful 2D/3D Visualization
Visual MODFLOW Flex’s powerful 2D and 3D viewers are capable of displaying high-resolution renderings of your model inputs and results. Using interactive viewer controls you can visually inspect and analyze your results from any virtually angle to gain the critical insight needed to deliver effective decisions.
Watch a short video that demonstrates the use of MODFLOW-USG to simulate groundwater flow for a simple 3 layer model in Visual MODFLOW Flex 2014.1.