open TELEMAC-MASCARET The mathematically superior suite of solvers

Dear all,

I am trying to modify the Qsform.f subroutine to implement the Karim and Kennedy (1983) sediment transport formula. However I am getting an error attached to the output.txt (GRADF not defined for IELEM1). I notied that if I set the SLOPE EFFECT=NO the simulation starts and finishes but there are a lot of NAN values.I am attaching the modified subroutines I am using in hope that you could help me.

I am trying to run the Yen example in the directory

Kind regards,
Andreas

Hello Andreas,

I think your problem comes from the bedload_formula.f subroutine. You added an extra-argument Q as input of the subroutine (between TOB and TOBW), without modifying the sisyphe interface, it can't works properly.
But I don't understand why you added this argument, you don't need to do it. Your case seems to work only with the qsform.f subroutine (and corfon.f). vitchu_sisyphe.f is also useless as you didn't modify it.

I hope it helps.

Regards,
Laurent

Thank you very much Laurent,

Indeed I overlooked that I didn't specify the variable Q (it was a leftover from a previous formula). However when I implement your suggestion the simulation runs, but I notice there are some NaN values at the bedload flux imposed at the boundary. What would be a possible reason for this occurence?

Kind regards,
Andreas

Andreas,

The problem comes from the term1 of your bed load computation. U2D/V2D can be negative. So when you raise this number to the power 2.97, ie exp(2.97*log(U2D)), log(negative values) gives you NaN numbers, not especially on the boundaries but inside your model domain.
I didn't know the formulation from Karim & Kennedy (1983), but you can look more closely at how they compute these terms. If it's not explained, you can try to take the absolute value of U2D/V2D to compute the term1 and then assign the sign of U2D/V2D to the QBX/QBY values.

I hope it helps.

Regards,
Laurent