Application of Newton iteration to the numerical solution of variable-density groundwater flow in saturated-unsaturated coastal zones

When addressing the question of variable saturation and density groundwater flow in coastal zones, highly nonlinear system coupled water-salt equations may deserve more attention. The classical Picard scheme is associated with slow calculation speeds low precision, which hardly meet actual needs users. Here, we developed a new numerical solution for issues based on Newton compared advantages disadvantages different methods by analyzing cases seawater intrusion. simulation results indicated that variable-density effect significantly extends computation time model, but still has computational speed better convergence scheme, especially conditions involving high-frequency large-amplitude tidal fluctuations, steep aquifer slopes, coarse grid. Furthermore, Newton-Picard method, schemes, improves robustness optimizes solution. This study revealed characteristics flow, providing ideas insights solutions to problems.