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Hello,

Telemac2d coupled with Sisyphe.

I am modeling a channel with flow deflectors through its length, with a solids discharge at inlet. The purpose is to study deflectors effect on erosion and deposition processes (trying to reduce sediment transport through the channel, using deflectors as a sediments traps). Flowrate at inlet and free flow at outlet as boundary conditions.

Problem using my hydrodynamics results as a Previous computation file.
When i run Telemac2d coupled with sisyphe with my previous computation file, the results are not good, the flowrate and the velocity increases really fast and the bed evolution does it too. Do not know why it happens. In fact, when i do not use a previous computation file the model works better, with an appropriate (logical) behavior. I have proven many things but do not get good results, i do not understand why, because i follow the telemac2d manual (Section 4.1.3).

In the screenshots you will appreciate the flowrate difference at inlet between Previous computation file and T2d coupled with sisyphe.

In the attachments you will find my cas files (Previous Computation: c1_t2d_hydro.cas, t2d coupled: c1_t2d.cas, sisyphe: c1_sis.cas), Geometry file bc_c1_t2d.slf, boundary conditions files: bc_c1_t2d.cli (the same for previous computation file and t2d coupled) and bc_c1_sis.cli.

Best regards,
Jose Morales
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+58 424 6551100
Venezuela

I could not attach results file of c1_t2d_hydro.cas, which is my previous computation file, but there is the cas and the geometry.

T2D BOUNDARY CONDITIONS FILE: Flowrate at inlet (4 5 5), free at outlet (4 4 4), both with no prescribed tracers.

SISYPHE BOUNDARY CONDITIONS FILE:
Inlet: 5 5 5 0 0 0 0 5 0 0 0 (Boundary 2) (Solid discharges).
Outlet: 4 4 5 0 0 0 0 5 0 0 0 (Boundary 1) (No bottom evolution).

Hello Jose,

Since you are continuing a coupled computation, why don't you also setup SISYPHE to continue from the previous computation? This way you pass information like solid discharges, bed evolution, layer thicknesses, rigid bed position, D50, etc, to the next computation. This is equally important to hydrodynamic conditions.

Regards,
Costas

Hello José,
I took a fast look to your files. There are some things to look-up:
(1) Your BC for T2D could be ill-posed. Why don't you impose the water level condition at the channel outlet?
(2) Which kind of flow do you have? Subcritical (Froude number < 1) or Supercritical? This can have an impact on the definition of the boundary conditions (some days ago Riadh posted a clarification on that).
(3) Your Sisyphe's file seems a bit incomplete. Please take a look to the Manual v7p2 and examples. Do you set your (equilibrium) solid fluxes = 0?
(4) Follow also Costa's post (thanks for pointing it out, I'll clarify this in the Chapter 1 of the Manual).

My suggestion:
- Run a clean hydrodynamics simulation
- Use that as hotstart of a Sisyphe's simulation, run in a 'traditional way', e.g. with Meyer-Peter and Muller.
- If the previous steps give physical results, re-adapt your steering file to your particular case.

Cheers,

Pablo

Dear Pablo and Costas,

Costas,

I will take in consideration your advice, in fact, i am running a model which runs fine. so thanks a lot.

Pablo,

About questions 1 and 2:
Effectively, you were right, my BC was ill-posed, but i already imposed water level condition at outlet and the problem disappear, and, about the flow, it is subcritical. I will take a look at Riadh's post.

About question 3:
I could not find the Manual v7p2, is it on this site?

About your suggestions (I will take them in consideration, as always):
Is possible to run a hotstart with non-erodible bottom? and then using it without any problem? or is this not recommended?

Best regards
Jose Morales
Venezuela

Hi José,
Please find below my comments.

Is possible to run a hotstart with non-erodible bottom? and then using it without any problem? or is this not recommended?
Yes you can. As always, take a look how your model behaves.

About question 3:
I could not find the Manual v7p2, is it on this site?
Humm, I don't know either. I'll ask...
Please drop me an email to This email address is being protected from spambots. You need JavaScript enabled to view it. and I'll send to you the pdf.

Cheers,

Pablo

Dear Pablo,

I am taking a look at the manual, but i would like to know:

How may i use suspended and bedload transport (both) in the same simulation? is that possible?

Also, with the inflow concentration, i supposed the quantity of suspended sediment is equal to Flowrate*Concentration, am i right?

Cheers,

Jose