open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello all,

I am running a model of the Irish Sea but I dont know which LAW OF BOTTOM FRICTION to choose. Can someone help me to choose between the 7 values offer by TELEAMAC? and explain me why please?

(or send me a link to a document. powerpoint etc... which can answer my question)

Regards

Jonathan

Hi,
personnally, I'm using Nikuradse's law and I'm calculating the ks= fac* D50 (fac: factor depending on the diameter of the sediment).

cheers

Hi flanagan,

Thank you for your answer but why did you choose Nikuradse instead of another?

Cheers

Hello Jonathan.
I also use the Nikuradse friction law for tow main reasons:

1. It allows bed roughness information exchange between sisyphe and telemac2d when coupled together
2. More intuitive. It has a direct relation to the roughness height of the bed, thus easier to calculate/estimate (from sediment grading, rocky protrusions etc)

Best Regards,
Costas

Hi Costas,

Thank you for your amswer. I dont work on sediment. I use the hydrodynamics model to study larvae dispersal, It sounds that Nikuradse seems the best how ever the domain of my model is so big that i dont know how to choose the best COEFFICIENT FRICTION?

Regards

In this case, TELEMAC employs several method's to define spatially varying FRICTION factors and/or FRICTION LAW's:

1. Add a variable named BOTTOM FRICTION to the geometry file, where you can define different friction factors using a pre-processing tool like BlueKenue
2. Use a friction data file. See paragraph 3.2.7 in the telemac2d user manual for detail on how to use it
3. Subroutines STRCHE and/or CORSTR, possibly with the aid of subroutine INPOLY to set a specific friction factor within closed polygons.

I find option one the easiest, using contour lines to define the variable friction factors and the interpolate to the mesh with BK. Option two is the only that can define spatially varying FRICTION LAWs.
Best Regards,
Costas