open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi everyone,

My questions are the fallowing :

I want to use the Nickuradse law, which is C= 7.83 ln(12h/ks) for the chezy parameter. What I want to know is how the roughness factor ks is calculate in Telemac?
What the meaning of the value in the option COEFFICIENT DE FROTTEMENT?
I understand that more my value is weak more I got rock bottom and in the opposite case it's sand/mud bottom. So can somebody tells me, in a more precise way, this meaning because i need to be more specific on the choose of that coefficient.

thanks in advance

Hello

To use the Nikuradze law, you have to set the keyword COEFFICIENT DE FROTTEMENT (LAW OF BOTTM FRICTION) =5.
In this case there are 2 options
1- If you are using only Telemac-2d: this value corresponds to nikuradze grain sizes
2- if you are using Telemac2d coupled with sisyphe: in this case, sisyphe can predict the bed friction by setting the keyword BED FRICTION ROUGHNESS=TRUE

I hope that this helps

with my best regards

Riadh ATA

hello

Thanks for your response. I would like also know the meaning of the friction coefficient in the case of the Chezy law?

thanks in advance

Hello,

If you look at subroutine friction_calc.f in library telemac-2D, you will see how the friction coefficient, given by the user and formula dependent, called CHESTR, is transformed into the usual non-dimensional coefficient CF.

With best regards,

Jean-Michel Hervouet