The initial fluid configuration consists of an inviscid fluid occupying the top half of a box that has a width of 1.0 and height of 3.0. Gravity is acting downward with unit magnitude. The free surface is given an applied pressure pulse,ps= cos(nx), that acts only during the first cycle of calculation. This pulse perturbs the unstable fluid surface, causing it to flow down along the right edge of the box in the form of a fluid spike, while a bubble moves up along the left box edge; see Fig. 10. During the earliest stages of growth, the amplitudes of the bubble and spike displacements follow linear theory [20], but nonlinear effects quickly take over with the spike growing simificantly more rapidly than the bubble.