This page shows solution to the wave equation in a unit square, where the quantity to be solved (displacement,pressure,etc.) has been given a nonequilibrum initial value (refer to the first figure) and integrated over time to solve the evolution of the system. There are no other forcing conditions in this model, and it's also assumed that no damping is present. The walls of the square are assumed fixed (reflecting).

Bilinear quadrilateral elements were used to obtain the solution to the wave equation.

Here you can download an animation of the results mpeg: [~2MB]