NUMERICAL COMPUTER SOLUTIONS
Computer models are used increasingly to make acceptable approximations for the Laplace
equation in complex flow conditions. The two primary methods of numerical solution are finite
difference and finite element. Both can be used for two-dimensional and three-dimensional
problems and software is available from several sources. Very simple problems can be solved
by hand, but more difficult problems require a computer. Both methods use a grid system to
divide the flow region into discrete elements. Element intersections are called nodes.
In either system, a series of linear algebraic equations are used to approximate the Laplace
equation. In the finite element method, if the grid consists of N elements, there will be N
equations in N unknowns to solve. Among the advantages of numerical methods are:
• Either two-dimensional or three-dimensional problems of very complex geometry,
including layers and stratification as well as pockets of material, can be modeled.
• Zones where seepage gradients or velocities are high can be more accurately modeled
by varying the size of elements.