open TELEMAC-MASCARET The mathematically superior suite of solvers

Dear community,

I have in my 3D model a small flooding area next to a channel. This area only gets flooded with storm surges and should stay dry in normal tidal conditions.The dike between the area and the channel is a single line of points, a so called chinese hat type of dike in the model. I know steep gradients can give rise to some problems and that it would be better to have at least two points representing the crest of the dike. But I noticed something strange. My flooding area gets filled with water and is filled completely till the crest level of the dike. This level is much higher than the water in the channel.

I made a very small test case where I divided a rectangle in to pieces. In the middle I put a chinese hat type dike; on the left side I kept the water level far below the dike level and the right side was empty at the start. After some timesteps the right side was filled completely till the crest level of the dike and far higher than the left side. When I put a double line of popints representing the crest level of the dike, this problem is gone.

What is happening here?

Kind regards,

Sven

Hello Sven,

This is the difficulty of wetting and drying algorithms when dry points on crests are influenced by wet points. There is a tentative solution with the keyword : THRESHOLD DEPTH FOR RECEDING PROCEDURE.

However I would be keen to have a look at your small test case, to see if we can have better ideas or a better tuning.

With best regards,

Jean-Michel Hervouet

Jean-Michel

I attached the files. The cas file is a simplification of the one we use for our big model.
For the big model I represented the crest level of the dike with a double line of points and the flooding area stayed dry.

I could understand that some water is going through, but found it strange that the area kept on filling till the crest level which is higher than the water level in the channel.

Thanks,

Sven

I think I forgot the cas file in attachments