open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,
I am currently working on the setup for an easy flume setup (at least I thought so). But at the hydrodynamic setup I have a problem.
It is a straight flume and I imposed a discharge rate at the inflow and the water level at the outflow as boundary conditions, like I always do. Telemac3d is starting the computation and it is running fine, but after more than 4000 time steps I get the error:
Problem on boundary 2 (which is the inflow), give velocity profile or check water depth
I do not know why I get this error, because the water level is at this time nearly steady at 0.1m, which shouldn`t cause problems. The MINIMAL VALUE FOR DEPTH is at the default value. I am working with Tidal flats with the default values.
Has anybody has a hint? Maybe I made some stupid fault and do not get the point…

Many thanks,
Gabriele

Hello,

This can only be explained if the depth at the entrance is 0 everywhere, which is not the case if you are right, OR if the prescribed velocities are 0 for some reason (depending on how the discharge is imposed or which kind of velocity profile you use). The subroutine that complains is debimp_3d.f (it replaces an older debimp3d that has been kept in the library for compatibility, so old subroutines bord3d may still contain a call to debimp3d). The minimum depth is -1000., so it should not interfere. Please note that you have also a keyword : THRESHOLD FOR VISCOSITY CORRECTION ON TIDAL FLATS which is by default 0.2, and that you should probably change in your case which is probably a physical model (it is not the reason of your problem, but may change the results).

Regards,

Jean-Michel Hervouet

Dear Jean-Michel,

thank you for the very quick answer. Yes, it is a flume test. I have checked the depimp_3d.f subroutine, but I have no clue why the velocities or the water depth should be zero.
I will change the threshold for velocities (thank you for that hint) and try a higher discharge.

Many thanks,
Gabriele

Hello,

OK. If you do not find, we would need to have your files to understand what happens, and try to prevent it for future users.

Say hello to my friends in the congress where I guess you are...

Regards,

Jean-Michel Hervouet

Hey Gabi!

Perhaps the answer is more easier because maybe you have supercritical flow at the inflow boundary?

Cheers
Clemens

Hi Jean-Michel,

thank you. I think the THRESHOLD FOR VISCOSITY CORRECTION ON TIDAL FLATS was the problem, because the case is now running so far.

And I will say helo to your friends

Many thanks
Gabriele

p.s. Clemens: Thank you for the hint, but the flow is really subcritical