Saturated-unsaturated seepage by numerical manifold method

The unsaturated seepage problem involves many fields, such as geotechnical engineering, hydraulic engineering and environmental engineering. So it is of great significance to simulate the unsaturated flow reasonably and effectively. Based on the cover system of numerical manifold method (NMM), a NMM discrete form is established to solve the Richards equation for the unsaturated flow. Compared with finite element method (FEM), NMM is more flexible in the preprocessing, and more adaptable to complex boundary conditions. By introducing the under-relaxation technique and the lumped mass matrix, the numerical oscillation is eliminated. Through the simulations of 1D and 2D unsaturated seepage problems, the validity and reliability of the proposed algorithm are verified.