open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

I'm simulating propagation of a solitary wave in TELEMAC2D with Q and SL as inflow boundary conditions in a rectangular channel of 9m length. The outflow is set to 4 4 4 (free flow boundary). However, I'm seeing some reflection in the results. I would assume the wave to propagate to indefinite distance without reflection if free outflow boundary is used. But, the model seems to somehow simulate the reflection. Could you please suggest possible error in my boundary conditions or work around? Thanks! All the simulation files are attached for reference.

Hi,

I'm not used to working with Boussinesq assumption but you can try to use Thompson boundary condition.

OPTION FOR LIQUID BOUNDARIES : 1;2

Alexis

Hi Alexis,

I have slightly changed the boundary conditions. Now the reflection is eliminated. But, the results are not as expected. The wave should propagate in the still water without much dissipation of wave height although change in shape is expected. I've attached initial wave height and wave height at 1m, 8m in the channel. We can see that the wave height dissipates rapidly and after the wave passes, the water depth keeps going down. I don't understand why (this doesn't happen when I simulate steady flow with same outflow boundary condition). The steady state (even when input specified as .liq file or prescribed elevations and flowrate) simulation seems to work well but not with waves. What could be going wrong in this case?

Thanks!

I went through your files, and I noticed that for the friction coefficient is 30 which seems too rough for 0.13 m deep water and this may have big impact, for example, for 0.25mm sand is about 104.

another thing is I dont see your FORTRAN file, did u program for Q and SL?

AMANJ

Hi Amanj,

I have tried varying the friction. Even very small friction coefficient of 0.0001 when Manning's law is used, is yielding similar results.

I was not aware of FORTRAN file requirement. Is it bord.f that needs to be modified? A sample fortran file required would be very helpful if you have one. Many thanks!

Ananth.

Hi Ananth,

The figures you provide are not conform the data in your csv file! Also the geometry.slf and results file are missing, so hard to see what is happening.
PS. I see you have outflow on your upstream boundary is this on purpose?

Hi Patrick, I have slightly modified the boundary nodes to eliminate the reflection, hence there is difference in figures and the excel previously provided.

I have the inflow on the right hand side of the domain and outflow at the left hand side. I followed this notation from the Baxter tutorial and defined my channel banks 'right' and 'left' with respect to the direction of flow at the inflow.

The result file is large to attach here. So I'm attaching the simulation files including geometry. If you could kindly run the simulation, it only takes 10seconds to run, you can examine the result file. I apologize for that. Many thanks!