The dispersion of the wave is quite strong and appears as wiggles behind the main fronts. This is due to the poor resolution of the initial pulse. The effect can also be seen in the original paper. A Neumann BC is applied at top boundary giving total reflections with 0 degree phase change. The first order approximation of the one way equation is applied at top boundary.
Some reflections are visible.
The second order approximation of the one way equation is applied at top boundary. Very litle reflections are visible. The first order approximation of the one way equation is applied at top boundary. The expanding cylindric wave is removed by solving the same problem on a larger domain and subtracting this solution from the one obtained above. The second order approximation of the one way equation is applied at top boundary.