DENSITY-DEPENDENT FLOW IN ONE-DIMENSIONAL VARIABLY-SATURATED MEDIA

A one-dimensional finite element model is developed to simulate densit y-dependent now of saltwater in variably saturated media. The Bow and solute equations were solved in a coupled mode (iterative), in a parti ally coupled mode (non-iterative), and in a completely decoupled mode. Pressure head was considered as the dependent variable in the fluid m otion equation, and a backward Euler scheme with mass lumping was used for time discretization of both flow and transport equations. The mod ified Picard method was used in the Bow equation to solve for pressure heads. The model was verified by comparison to an analytical test fun ction and published numerical results. It was found that density effec ts on the Bow decreased with the pressure head. However, significant e ffects can still be observed at relatively low (negative) pressure hea ds. The density dependence effects were st their maxima at steady stat e. Partial coupling of the flow and transport equations was shown to g ive satisfactory results in comparison with full coupling. The advanta ge in partial coupling is a reduced amount of numerical computation. T he finite element formulation of the model is presented in a form that allows a person with finite difference expertise to implement it easi ly. (C) 1997 Elsevier Science B.V.