Simulation at time t=0.2 using front tracking and dimensional
splitting with grid refinement.
Discretization parameters from top to bottom:
Dx = Dy = (1/30, 1/60, 1/120).
Number of equally spaced time steps:
70, 140, and 280.
Local refinement by a factor two in each direction.
Fraction of refined blocks at final time:
54%, 35%, and 21%.