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Hi all,

I was wondering about how the friction velocity US (in the graphical output variable) is calculated? I searched in the manuals but didn't find it.

Can it be linked to (or is it?) the bed shear stress velocity? That would be interesting to forecast possible erosion areas without knowing the sand characteristics (if US bigger than critical velocity for those sizes of grain then erosion from those classes possible...)

Would anyone have a clue?
Thank you in advance!

Jean

Hello Jean,

yes, it is the shear velocity. You can find the calculation of this source term in the mathematical reference manual Telemac-2D version 3.0, 2001.

Best regards,
Clemens

Thank you Clemens for your prompt answer, do you know where I can find this manual?

Mit freundlichen Grüssen
Jean

Hello,

This manual is now replaced by the book "hydrodynamics of free surface flows". The friction velocity is : sqrt(Cf * (u**2+v**2)) where u and v are the components of velocity and Cf is the non dimensionnal friction coefficient. I added it in the outputs on request of sedimentologists.

With best regards,

Jean-Michel Hervouet

Hello all,

As a followup to this question.
The latest version of Blue Kenue has some post processing functions (under Tools->BedTools->) that allows you to generate temporally varying Shear Stress maps from HD output.
You supply currents and (depths if appropriate) and bed roughness either as chezy, mannings N, strikler or grain size.

Cheers... Martin