A novel modeling approach using arbitrary Lagrangian-Eulerian (ALE) method for the flow simulation in unconfined aquifers

The problem of groundwater flow in an unconfined aquifer, formulated as a free-surface problem, is solved numerically through a new approach by employing the arbitrary Lagrangian-Eulerian (ALE) method. The domain of interest is three dimensional or a two dimensional vertical cross-section of a phreatic zone of an aquifer, where the groundwater table is the upper boundary that is allowed to move. The ALE method allows capturing the location of the free-surface by transforming the moving domain to a fixed reference domain through arbitrary forced boundary conditions. The results of the verification runs of this new approach agree well with the known analytical solutions for aquifer characterization tests. Beside the comprehensive and accurate evaluation of the groundwater flow in the tested cases, the approach is also suitable for modeling complex situations. The implementation of our method for selected cases is illustrated by means of practically relevant examples.