Numerical simulation of density-dependent saltwater intrusion in sandbox model

Numerical simulation is a widely adopted tool for understanding saltwater intrusion in coastal aquifers, simulating density-driven solute transport processes in porous media. However, most of these simulations exclusively model only groundwater flows and are mesh-based solvers, which may pose challenges for complex geometries. Here in this paper, we present an incompressible smoothed particle hydrodynamics (ISPH)-based combined surface–groundwater flow model for predicting density-driven flows in aquifers. The model consists of a modified momentum equation solution for less restrictive Courant–Friedrichs–Lewy (CFL) conditions when dealing with low-permeability sediments and taking into account viscosity variation. The developed ISPH code is validated using two benchmark problems to ensure acceptable performance with regard to the model’s ability to simulate physics of flow through porous media and density-driven flows. Simulations are performed for an unconfined and confined aquifer spanning a time period of 7320 s and 5220 s, respectively, the obtained numerical results were compared with experimental solute transport observations, and they were found to be in close agreement with each other. The calibrated hydraulic conductivity and dispersivity values are significantly lower than values obtained from solvers that simulate only groundwater flows, and our numerically calibrated values are much closer to real-world values for porous media.