Modeling three-dimensional free-surface flows using multiple spreadsheets

In this study a spreadsheet application of three-dimensional seepage modeling with an unknown free surface has been carried out. The governing equation is derived using finite differences method in the general case of anisotropic and non-uniform material properties and variable grid spacing. The derived finite difference equation is also modified by the extended pressure (EP) method in order to reduce variational inequalities to simpler equalities. One of the main advantages of this study is that only one finite difference equation has been applied to the solution domain instead of derivation of additional finite difference equation to impervious boundary conditions, inclined interfaces, etc. The technique is illustrated by two free-surface seepage problems and good agreement is obtained.