A PARTITIONED SOLUTION PROCEDURE FOR SIMULATING WATER-FLOW IN A VARIABLY SATURATED DUAL-POROSITY MEDIUM

A simple and computationally effective partitioned solution procedure was used to solve the coupled equations of water flow in a variably-sa turated dual-porosity medium. The coupled equations were first discret ized in space and time using standard numerical solution procedures. T he resulting algebraic system was subsequently partitioned in the time domain with a staggered implicit-implicit partitioning scheme. The pa rtitioned time-integration procedures were carried out sequentially fo r the two subsystems, and coupled by temporal extrapolation techniques . A numerical stability and accuracy analysis demonstrated that the pa rtitioned solution scheme, when integrated with the midpoint rule, is unconditionally stable and second-order accurate with only a single-pa ss through the partitioned equations (i.e. without iteration between t he two subsystems). Simulation examples revealed that the solution of the single-pass scheme yields a slightly delayed response to that of t he iterative scheme.