open TELEMAC-MASCARET The mathematically superior suite of solvers

hey all
i am working on a channel.
the simulation ends well but i get zero velocity in results file.
the reason is that while running
GRACJG<BIEF>: SOLUTION X=0 BECAUSE L2-NORM OF B VERY SMALL: 0.19901E-21

please tell me where i am heading wrong.

Regards..

liquid boundary file

T Q(1) SL(2)
s m3/s m
0 690 1578.34
5000 430 1585.67
10000 450 1586.4
15000 720 1589.23
20000 410 1585.199

Hello,

In your case boundary 1 is the exit (first appearing in the boundary conditions file) and boundary 2 is the entrance. So you need to give SL(1) and Q(2) and it should work.

With best regards,

Jean-Michel Hervouet

hey Michel

I checked thoroughly. Boundary 1 is the entrance and 2 is exit.
am i inferring reverse from the input?

i checked with ua suggestion anyway and it ends with an error problem on boundary number 2, give a velocity profile in boundary conditions file or check the water depths.

Hello,

Hum, what did you really check? By definition the boundary one is the first appearing in the boundary conditions file, as I told you in my previous post, and what I see in this file is that the first liquid boundary has 5 4 4 conditions, thus depth imposed and free velocities, thus is an exit!

Then the problem of velocity profile on boundary 2 (the entrance) is an other problem, probably due to the initial conditions, you should have water on this entrance, otherwise the flow will be supercritical and the depth must be prescribed also.

With best regards,

JMH

The channel mesh gives the option for left and right bank. Doesn't that specify the entrance and exit?

Anyhow, how do i set boundary 1 as entrance?
I am new to this software, these might be silly questions but please help.

thank you

Regards...

Hello,

You do not set boundary 1 as entrance. Your boundary on the left of the channel is number 2 and if it is your entrance give the discharge Q(2) in your file. The boundary on the right is number 1, so give SL(1) if it is the exit. Then you will have the problem of initial conditions to solve, what are the initial conditions ? I suggest a constant elevation equal to the elevation at the exit at time 0.

Regards,

JMH

Hey

I think i m getting all this wrong.
the left and right i was talking about earlier are the closed boundaries.
the open boundaries here can't be differentiated as left or right sided. Right?

yes initial condition is as u said.


Thank you for reply.

Regards..

Also change your steering file with :

TREATMENT OF THE LINEAR SYSTEM : 2
OPTION FOR THE TREATMENT OF TIDAL FLATS : 1
DISCRETIZATIONS IN SPACE : 11;11

to start with. I see that you do have a constant elevation as initial conditions, try 1575.89 instead of 1576 for the initial elevation, also remove useless spaces in the line INITIAL CONDITION... because it has more than 72 charecters.

Regards,

JMH

Hey
I made all the changes you suggested.
But the error is still persisting.

Please help me out here.

Thanks

Regards..