The following specific case of the GAMM workshop  is studied here:
total length of channel .
length inflow section .
total height .
height inflow section .
maximum flow component of parabolic profile in inflow section .
the flow volume is .
The result for the minimum x-velocity at distance behind the step is studied. This result checks the correct modeling of the recirculation zone after the step. At the distance we find the minimum velocity is . This happens at above the lower edge. The results of the GAMM workshop were in between and .