open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

trying out some modifications with the skin friction correction factor I detected some small inconsistencies between coefro_sisyphe.f and tob_sisyphe which could be repaired quickly.
And assuming that the whole code works with Karman constant = 0.4:

In coefro_sisyphe.f given the value of 11.036D0 (=30/e = e^(8.5*0.4)/e in the computation of the quadratic friction coefficient based on the Nikuradse roughness, in tob_sisyphe the values 12.D0 should be replaced with the former one. The value of 12 is still based on the Karman constant of 0.41.

Best regards,
Clemens

Hello Clemens,

Very good remark, this will be done in the trunk for the next release. By the way I notice that according to the origin of 30, it is also an approximation since it should be 29.9641 ? (this is just for my personal understanding...).

With best regards,

Jean-Michel Hervouet

yes,

as you know, in the textbooks commonly the value of 29.9641 is approximated as 30.
I think the important thing is to be consistent:
e.g. if the user specifies a nikuradse roughness of ks=3*d50 and a grain diameter of d50, then the default Sisyphe setup (skin friction correction on and ks' = 3 (KSPRATIO) *d50) should give a skin friction correction factor of exactly 1.0.

Best regards,
Clemens