open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi to all,

I am trying to run a simulation for a river section and it works just, if I define an initial condition. Otherwise I get an error message on my discharge boundary condition. So I started the simulation with an intial depth of 1 meter. But is there also an option to run it from the beginning "dry".

Besides I checked some cross sections and I got the attached image. Why is there water on the bathemetry slope? Is there something wrong in the parameters of the simulation?

Thanks in advance.

Hi
It's impossible to impose a discharge on a dry section with telemac.
If you want to start with a dry model, you could start your simulation with no water but you should impose for few time steps the water level and the velocity at the upstream boundary (you could also imposed only the water level but in such case you don't have any control on the discharge). After those few time step, you could make a hot start with an imposed discharge.

For the image of cross section, the water on slope is partially due to the drawing method. When there is no water (H=0), the free surface is equal to the bottom so when the program make a linear interpolation between a dry and a wet point, you could see an artificial slope...

Hope this helps

To complement Christophe's answer, you can also use SOURCES, especially if you need to control the discharge. You can choose a node downstream of your inflows, not too close to your boundary segment, and discharge on dry as a SOURCE.

Because SOURCEs are added in the (water) mass conservation, it is easier to take them into account when you start with dry land.

Also, if you are more worried about level at your upstream boundary, you can add a small reservoir (part of the mesh), deep enough not to be dry. You can then set the level and the water will spill over into your dry land.

Hope this helps.

Sébastien

For the second question (again to complete Christophe's valide observation), it is recommended that you mesh across the top of your dykes with at least 2 nodes, and even better with 3 nodes (the middle one being slightly higher. It should help with any leaking water if there is any.

Hope this helps,

Sébastien