open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello

I'm using Telemac 2D with a possibility to modify the elevation of bathymetry/topography between two time steps.

I have two questions :

1- Is the subroutine “survol.f” used for each time step ?

2- I would like to use for each time step, the wet area of all elements (triangle) which are not completely wet.
Is there a subroutine to do this calculation or a easy way to define this wet area ?

Thanks

christophe

Hello,

Subroutine survol is called only once and is only the quantity 2/(area of triangle), the area of a triangle I is found in MESH%SURFAC%R(I)

Telemac-2D has only the knowledge of "wet" or "dry" for the elements, it is given in array TE3 at the exit of subroutine DECVRT called in propag.f. 0.D0 is for dry and 1.D0 is for wet. A dot product of this coefficient and MESH%SURFAC%R would give the wet area.

Another possibility is to choose a threshold depth HMINI for deciding whether a point is dry or not. Then if H%R(I) > HMINI the area VOLU2D%R(I) would contribute to the wet area. VOLU2D is the integral of test functions, which are in fact a kind of area around each point.

I hope you find a way with this,

Jean-Michel Hervouet

Hello Jean Michel


thanks for your answer.

I 'm not sure I understand well what is VOLU2D but I understand that VOLU2D is attached to a node. I think this creates me a problem because I want to use the wet area of the triangular elements which have one (or two) dry node : How to define the wet area of an element of this type from the values VOLUD2D of two (or one) wet nodes ?

Your first solution seems interesting too, but I think understand that a dot product of MESH%SURFAC%R with TE3 would give me the total area of the elements which are totally wet, this is not what I m looking for. Am I right or I've missed something ?

Thanks a lot for the precisions !!

Christophe

Hello,

The wet area of triangles which have only 1 or 2 dry nodes is zero if you admit linear interpolation of finite elements, and you need also a threshold to define wet or dry, so I am not sure of what you want to do. However we tried to answer this problem with the porosity option, see subroutine poro11.f in library telemac-2D. However this is all based on assumptions. For example if you assume that the free surface is flat and know the quantity of water in the element, this should be possible.

R<egards,

Jean-Michel Hervouet

I m trying to estimate a mean shear stress on partially wet element. To do this I would use the ratio wet area/ total area.

I will look the method of calculation of percentage of inundated in subroutine poro11.
Is it this subroutine automatically used by TELEMAC 2D ?

Thanks

christophe

Hello,

No, this subroutine is called only with option 3 of the treatment of tidal flats, it is the "porosity" option, which speeds up a bit the flood waves.

Regards,

JMH

Dear Christophe

The subroutine survol is used to compute the area of an element of the mesh, such as triangle (in your case). As far as I know, it is called once at the initialization step. However, you can call it at any time you want through the fortran file.
Your second question is a little more complicated. An element which is not completely wet is described differently whether you think numerically or physically. Physically the separation between dry and wet areas is well described by line (straight or curvilinear). However, numerically, an element is partilly wet (or dry) when one or two nodes are not wet.
The destribution of the quantity of water on the element depends on the numerical approach you are using (Finite elements or finite volumes, which order in space ...) but also on the wetting/drying algorithm implemented within the code. Thant's why you can not identify the wetted area in these elements.

I hope that this can help you
Best regards