open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello everyone,

I recently tried to simulate steady-state wind-driven currents in an estuary using Telemac3d. The triangular mesh with approximately 200 m resolution consists of 8742 elements. In the vertical direction 14 layers were applied similarly to "vent" example. I'm attaching here cas-file and would like to ask a few questions:
1.Results showed that there were abnormal zones with very high turbulent energy values (picture 1). Could you please suggest the solution for avoiding them? (I believe they might be a cause of increasing the computation time due to excessive iterations).

2.Velocities on the surface look strange (pictures 2,3). In this case of stationary lateral wind I expected them to be of higher magnitude on the shallow eastern and western coasts than on the deep central part.

I would much appreciate any insights and suggestions.

Kind regards,

Dmytro

Hello,

A few remarks on your case:

* With the k-epsilon model COEFFICIENT FOR VERTICAL DIFFUSION OF VELOCITIES should be equal to 1.E-6.

* The abnormal value of turbulent energy seems to be on a dry bed. Given your geometry with steep banks it is probably not useful to have dry zones in your model, you could have boundaries with a minimum of water so that you do not have to treat dry zones.

* There is a threshold depth for wind" set at 1 m, this could explain why you do not have velocities near the banks. You can change this keyword.

I hope this helps,

With best regards,

Jean-Michel Hervouet

Dear Jean-Michel,

Thank you very much for your suggestions. I've changed a threshold depth for wind and vertical diffusivity coefficient. Unfortunately, when I switch off the treatment of the dry zones (TIDAL FLATS =NO) the model fails to run with the following error:


I thought that the cause of the problem might be a steep bathymetry in the domain. I tried various vertical layering schemes with different number of fixed planes (TRANSF_PLANE =3) and sigma-layers (TRANSF_PLANE =2) but to no avail. The issue still persists but I will be working on to resolve it.

Kind regards,

Dmytro

Hello,

You seem to have negative depths that create the problem, is it right that you have tidal flats or dry zones?

In this case you can try :

TREATMENT OF NEGATIVE DEPTHS : 2

to get depths strictly positive or 0.

With best regards,

Jean-Michel Hervouet