open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,JMH,
I visualize the calculation result. The velocity result is in the attachment file. I think there is some problem about that. What do you think about that?
Best regards.
Jinyong ZHAO

Hello,

If it is the norm of velocity, it tends to have oscillations at the exit. Try to stabilize it with a lower FREE SURFACE GRADIENT COMPATIBILITY, or with a higher diffusion of velocity (also check the prescribed elevation at the exit). Probably it is the free surface elevation that has inf-sup wiggles. The lateral branch would be better treated with an upstream boundary at exactly right angle, because the entering velocity is given normal to this boundary. Your case is very standard and you should get good results.

With best regards,

Jean-Michel Hervouet

Hi, JMH,
I do the simulation in two scenarioes.
Scenario1:FREE SURFACE GRADIENT COMPATIBILITY=0.9;VELOCITY DIFFUSIVITY=1.E-3
Scenario2:FREE SURFACE GRADIENT COMPATIBILITY=0.01;VELOCITY DIFFUSIVITY=5.E-3

In scenario1,there is serious oscillation at the exit.
In scenario2, the phenomion of oscillation is little improved, however, I notice the following information on the screen printout, which indicates that there is big difference between the discharge of flux boundary1 and the sum of boundary2 and boundary3.
BALANCE OF WATER VOLUME
VOLUME IN THE DOMAIN : 3.384797 M3
FLUX BOUNDARY 1: -0.1097212E-03 M3/S ( >0 : ENTERING <0 : EXITING )
FLUX BOUNDARY 2: 0.3499937E-01 M3/S ( >0 : ENTERING <0 : EXITING )
FLUX BOUNDARY 3: 0.7000062E-01 M3/S ( >0 : ENTERING <0 : EXITING )
RELATIVE ERROR IN VOLUME AT T = 0.2500E+06 S : 0.3097318E-02

I attach the screen information and the velocity calculation result of the two scenarioes.

Thanks.

Jinyong Zhao

Hello,

VELOCITY DIFFUSIVITY = 5.E-3 is still very small, in real rivers it can be 0.1 or 1 m2/s

To have an exact mass conservation, increase the accuracy of solver and do not forget to use :

CONTINUITY CORRECTION : YES

otherwise the fluxes on points with prescribed elevation are not very well computed (at these points the continuity equation is replaced by equation elevation = given elevation).

With best regards,

Jean-Michel Hervouet

Hi, JMH,

I try with several scenarioes with di
fferent values of FREE SURFACE GRADIENT COMPATIBILITY and VELOCITY DIFFUSIVITY, however, I think the result of velocity are not very reasonable. In the attachment file, I collect all of them. In the title of attachment files, "surface" means FREE SURFACE GRADIENT COMPATIBILITY, and "ve diff" means VELOCITY DIFFUSIVITY.

Best regards.

Jinyong Zhao

Hi, JMH,
I try to review the process of the error. And, I try layer.f in the steering file.
I have two steering files. One is related with flow calculation, and another is related with sediment calculation.
I add "FORTRAN FILE=layer.f" into my steering file related with sediment calculation.
When running, the error information is "ERREUR A L'ACQUISITION DU FICHIER layer.f ". How to solve this error? and how to change the ZERO given in DATA?

Many thanks.

Jinyong ZHAO

Hello,

The FORTRAN FILE may have any name and you can put inside a copy of the subroutine layer.f, but it must be in the folder of your case. So:

Create a file princi.f, put inside a copy of subroutine layer.f, put this file princi.f in your case folder, and declare in the Telemac2d steering file :

FORTRAN FILE : princi.f

and that's it. I am not sure that if there is no FORTRAN FILE on Telemac2d side you can have one for sediment transport. Anyway both are merged by the scripts.

Regards,

Jean-Michel Hervouet