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:
Case Study: MODFLOW-USG Yields 90% Reduction in Run Times for Regional Groundwater Model

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 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.