open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello everyone!!

I am testing the model with impermanent flow in a section of the Paraná river between the cities of Puerto San Martin and Rosario. The upstream boundary condition was represented with a inflow hydrograph [Q(t)]. Downstream was defined a curve representing discharge versus water level [H(Q)].

Previously two meshes were defined. One with elements of size equal to 100 meters (M1) and another of 50 meters (M2). Thus the mesh M2 is more discreet than the mesh M1. Both constitutions were calibrated for permanent flow. The first constitution (M1) was calibrated for a roughness equal to 0.023 and the second one for a roughness equal to 0.025. Water levels recorded in two hydrometers were compared with calculated water levels. Both constitutions adjust their results well.

Then we performed the simulations for impermanent flow. The constitution M1 ran with a roughness of 0.023 and a time step of 1 second. The constitution M2 ran with a roughness of 0.025 and the same time step.

The figure shows a comparison between the water levels recorded in the two hydrometers and the water levels calculated in both constitutions for the simulated time period. In black the water levels recorded in the hydrometers are detailed. In blue the calculated levels for the constitution M2 and in pink for the M1.

Is it possible for the less discrete mesh to reproduce better the measured levels? The calculated levels for constitution M2 do not fit well at all. It seems that something is wrong but I can not find the error.

Hi Flor.

Can you check and display if the cross section are the same or if the coarse discretization lead to a bad representation of the Xsection.

Are you sure that the discretization is the only parameter that changes between the two cases? What about the rating curve?

Alexis

thank you very much!!

I think I have a problem with the downstream boundary condition H-Q. Now I ran the program for permanent flow with two options:

* The upstream boundary condition is incoming constant flow (Q = 19570 m3/s). That's why I use an Open boundary with prescribed Q [Q(t)]. Downstream was imposed a fixed water height of 6.60 m. That's why I use an Open boundary with prescribed H [H(t)]. The calculated water levels and the water levels that were registered in the hydrometers are very similar.

* The upstream boundary condition is incoming constant flow (Q = 19570 m3/s). That's why I use an Open boundary with prescribed Q [Q(t)]. Downstream was imposed a curve indicating Discharge - Water Surface Elevation (H-Q). That's why I use an Open boundary with prescribed Q and H. Now the calculated water levels are 1 meter above those observed.

For the flow of 19570 m3/s in the vicinity of the downstream boundary does not approximate the value indicated by the curve H-Q for that flow (6.60 m). The model stabilizes for a water level downstream equal to 8.10 m.

I send the .cas file that I use (Parana.cas) and the file of upstream and downstream boundary conditions (hydrographs_Parana.liq and rating_curve.txt).

the .liq file:

#Open boundary file created for T2D simulation;
#Inflow hydrographs
#
T Q(2)
s m3/s
0 19570
86400 19570
172800 19570
259200 19570
345600 19570
432000 19570
518400 19570
604800 19570
691200 19570