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Hi,
I used the "friction data file" method for to assign different friction co-efficient for different zones in a single domain in my old simulation (using the method mentioned in the tag "How to define friction coefficient by domain) to check whether it is working fine or not, but it gives me really high velocity (almost 10m/s higher) and all.

I used the same friction law and co-efficient which I used previously but it's not working.I'm not able to find the reason.

Can anyone help me?

Thanks,
Sathish

Hello

Can you send us both models so that we can debug this issue?

with my best regards

Riadh ATA

Hello,

I had a look at both cases and what I see is not what you say in your post, please be more specific. In the "old" case I see a constant Chézy coefficient equal to 35., in the case "new" I see 6 zones of Chézy friction with coefficients ranging from 70. to 200., so this is less friction and you have accordingly larger velocities, that's all I can say. It is a case of a tide in a bay with very shallow flows in the upper part of the mesh, so probably high velocities when the tide comes in and high influence of friction.
The accuracy you ask for is also probably too rough, try 1.E-6 instead of 1.E-3.

With best regards,

Jean-Michel Hervouet

Hi JM,

Initially, I tried with constant bottom friction, after that I assigned spatially varying friction in the GEO file. Please check the geo file which is having a bottom friction coefficient ranging from 70-200, and the coefficient in the CAS file is not considered during the simulation, it takes the coefficient which is given in the GEO file.

Thank you,
Sathish

Hello,

Sorry, I missed that, so I look again...

JMH

Hello again,

OK, so I looked at the file, and actually what should be the friction coefficient is instead the zone number from 1 to 6, isn't that the problem ?

Regards,

JMH

Hi JM,

I followed the procedure given in the example file to create a zones and roughness file!

I used same friction coefficient values for the 6 zones in both the cases( old and new sim) but different method. But it is giving me strange results!
I don't know why?

Why it's giving me high velocity and surface elevation in the new simulation when I use the different method to specify the friction coefficient?

Is there any problem in the zone definition file or roughness file?

Thanks,
Sathish

Hello,

There are two problems in your case 'OLD' :

1) the geometry file has a variable named "Coefficient frottement de fond". This name is not recognised as Telemac (in subroutine fonstr.f of library bief) expects the names FROTTEMENT or BOTTOM FRICTION, in 32 characters.

2) this variable "Coefficient frottement de fond" obviously has been filled with the zone numbers from 1 to 6, while the coefficient itself is expected.

The result of 1) is anyway that this variable is not read and the program takes the value of 35 given in the steering file.

My question is: where did you find information or an example saying that you should have a variable "Coefficient frottement de fond" containing the zone numbers ?

WIth best regards,

Jean-Michel Hervouet

Hi,

I don't know what went wrong. I never used French keywords and I checked the geo file but it shows BOTTOM FRICTION only

I attached the example case which I followed.

Hello,

OK, I got it ! I looked at the files with Fudaa and Fudaa gives me a translation of the variables in the file !!!!!!!!!!!!!!!! (what a strange idea from the developer !!!!)

We really have (if I look with Tecplot):

File GEO_02.slf (case new) has "BOTTOM FRICTION" with zone numbers from 1 to 6.

File GEO_large_GK_BF_01.slf (case old) has "BOTTOM FRICTION" with coefficients from 70 to 200.

So I have to restart from scratch... sorry...

With best regards,

Jean-Michel Hervouet