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Hi all,
I'm trying to make a numerical model using variable bottom friction in space. I used Fudaa prepro to define the bottom friction coefficient on each node (on a 59155 nodes mesh). I'd like to know if I should use the FRICTION DATA parameter in the steering file and a friction data file or if I should use a subroutine in the fortran file ?

Best regards,

Damien C.

Hello,

The friction data file is rather meant for different zones with friction constant within each zone. You can use also :

subroutine STRCHE (library bief) : there you can build your friction coefficient as you like.

subroutine CORSTR (library telemac-2D) : it is called at every time-step so useful if your coefficient varies in time.

With best regards,

Jean-Michel Hervouet

Hi

If your friction coefficient is constant in time and only variable in space, the easiest way (no fortran subroutine) is to use FUDAA-PREPRO like you seems to do it.
You just have to activate initial condition, add the friction coefficient to the variables and define the node value.

Regards

Thanks for your answer,
In "activate initial condition, add the friction coefficient to the variables", does it mean I only have to add (in my steering file) the 'W' variable in "VARIABLES POUR LES SORTIES GRAPHIQUES" and use "COEFFICIENT DE FROTTEMENT VARIABLE EN ESPACE = OUI" ?

Regards,

Damien C.

Not exactly
Adding W in "variables pour les sorties graphiques" just gives you the possibility to draw the friction field as a result.
In the 2D editor, you activate the initial condition and the in the node layer, you add the friction. After that, you could modify the value.
It seems to me that there is an example on the fudaa website (in french)
regards

Hi all,

I am trying to insert friction zones in my project using Fudaa.
I checked the info (manuals & videos), but I still wonder about some precisions:

-do we have to initiate the initial conditions first of all? is it better to do it with a free surface or a result file?

-is there a special name to be given to the nodal attribute (coefficient de frottement de fond?), so that the software would be able to recognize and load it?

-the keywords DEFINITION DE ZONES should be checked?

Thank you in advance!

Best Regards,

Jean

Hello,

the keyword 'DEFINITION DE ZONES' is used only if you want to fill an integer array called ZONES (a BIEF_OBJ structure, so data are in ZONES%I). To fill ZONES you have a subroutine called DEF_ZONES, and then this array ZONES can be used wherever you want, using e.g. the following statement :

USE DECLARATIONS_TELEMAC2D, ONLY : ZONES

However this is not useful if yo use Fudaa.

Regards,

Jean-Michel Hervouet

Hi,

I tried to set the bottom friction coefficient using fudaa. I followed the instructions given here and in fudaa's user manual.
The enclosed graph shows 2 hydrographs drawn on the same profile with the following configurations:
- K = 10 everywhere defined using fudaa,
- K = 10 everywhere defined with keywords in the steering file.

Obviously, something has went wrong...
For the "K with fudaa" computation, i removed the "COEFFICIENT DE FROTTEMENT" and "LOI DE FROTTEMENT SUR LE FOND" keywords from the steering file.
With such configuration, how can telemac know that my mesh K values correspond to the Strickler law ?

Thank you in advance,
PL

Hello,

You should not remove the 2 keywords from your parameter file. The law of friction will be kept, and the friction coefficient will be ignored, you can see in subroutine FONSTR in library bief how it is programmed (look for logical CALFRO). User subroutine STRCHE has priority over the friction in the geometry file, which has priority on the constant friction given by keyword.

With best regards,

Jean-Michel Hervouet

Ok, I understand now the CI will be loaded in the geometry file and the attribute 'coefficient de frottement de fond' is already given.
Sorry for that!

Regards,
Jean