A finite-element algorithm for modeling variably saturated flows

A general numerical algorithm in the context of finite element scheme is developed to solve Richards equation in which a mass-conservative modified head based scheme (MHB) is proposed to approximate the governing equation and mass-lumping techniques are used to keep the numerical simulation stable The MHB scheme is compared with the modified Picard iteration scheme (MPI) in a ponding infiltration example Although the MHB scheme is a little inferior to the MPI scheme in respect of mass balance it is superior in convergence character and simplicity Fully implicit explicit and geometric average conductivity methods are performed and compared the first one is superior in simulation accuracy and can use large time-step size but the others are superior in iteration efficiency The algorithm works well over a wide variety of problems such as infiltration fronts steady-state and transient water tables and transient seepage faces as demonstrated by its performance against published experimental data The algorithm is presented in sufficient detail to facilitate its implementation (C) 2010 Elsevier B V All rights reserved