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hi everyone

I understand that it is not advisable to use supercritical flows in edge conditions.
"Is it because of the instability of the equations?"
- Is there a number of Fr where there is no problem in modeling supercritical flows?

Since I had to model supercritical flows, I create stretches at the beginning and end where in subcritical conditions, but when using sisyphe these stretches affect me to the balance of the system, how to solve this?

thanks

Hello,
What do you mean with "edge condition"? at boundaries ?

For the hydrodynamics part, you can probably try a different numerical scheme. Finite volumes could be more suitable to your problem.
Once you have solve that, we can start discussing about the morphodynamics part...

cheers

pablo

Pablo,

Sorry, yes, I meant the boundaries.

I think I express myself wrong in the question or I do not understand your answer.

I want to study sediment transport in a section where the flow is supercritical. In the previous topics of the forum, you advise not to use border conditions for supercritical flows (I do not know the reason for this and in which the number of Fr can influence), that's why I created a section at the beginning and the end where El Flow is subcritical. Hydrodynamics is correct.

Now, when studying morphology, these additional stretches in the study (beginning and end) influence the balance of the system, modifying sediment transport where I really want to know (supercritical section).

Attached image of my problem.
Red: Bottom Inicial
purple: Bottom equilibrium

Dear Jegatam,
A word of caution: dealing with transcritical and supercritical flows can be a bit tricky for morphodynamics problems. Under these flow conditions, the characteristic time scale for the propagation of bed waves is comparable to that of free-surface waves. As your Froude number increases and goes far beyond the value of one, the validity of the decoupled approach (solution of the SWE, then the solution of the Exner equation) may be not longer valid.
Anyway, and with this on mind, it could be interesting to see how your model behaves under these conditions.
A suggestion could be :
1. to have a nice hotstart (hydrodynamics) condition
2. to impose rigid bed in your "buffer" zone

Some references below:
J. Sieben. A theoretical analysis of discontinuous flow with mobile bed. Journal of Hydraulic Research, 37(2):199–212, 1999.
D. A. Lyn and M. Altinakar. St. Venant-Exner equations for near-critical and transcritical flows. Journal of Hydraulic Engineering, ASCE, 128(6):579–587, 2002.