Dam break // wet bed
 

Consider a horizontal and frictionless channel, which is 1000 m in lenght. A dam site is located at 500 m. The initial upstream-water depth is 10 m, and downstream-water depth is 6 (or 2 or 0.1 m).The vertical dimension of gaz layer is 3m. At time t=0, the dam is broken instantaneously.

I use a space steps of 10 m (100 cells )in horizontal direction and 1 m (10 cells in upstream-water, 6 cells in downstream-water and 3 cells in gaz layer) in vertical direction. A time step is 0.3 s.

I work with a (2-D) model and using implicit scheme for time and hybrid scheme for convection terms.

I use SEM method for this case but I don't have a best results compared with analytical solution so,

1- Is it the problem in the time step (CFL condition).

2- The simulation shows that the gaz layer has an influence on the free-surface profile; How I should impose the vertical dimension of this layer.

3- What is the significance of the velocity field in the gaz layer.

Thanks