open TELEMAC-MASCARET The mathematically superior suite of solvers

Dear all,
As you can see in attached photos, I'm trying to simulate a simple flow case on a channel of 140m with combined cross-section. I imposed a Q equivalent to a 1,40m of water head based on uniform condtion relations.

I would like to know more details about the equations which calculating the water depth at liquid boundary condition in particularly in the outlet of the channel. How water goes out from the channel? What is the hydraulic convey condition at the end of channel? Critical depth?

Why the water depth reducing in the channel going through downstream? Even if I impose a high water level the same as upstream?

Choosing option 1 in liquid BC as 'notmal condition' refers to which equations?

Hereafter the cas parameters that I use:

VARIABLES FOR GRAPHIC PRINTOUTS = 'U,V,S,B,F,H,W,US'
GRAPHIC PRINTOUT PERIOD = 50
LISTING PRINTOUT PERIOD = 50
TIME STEP = 0.1
NUMBER OF TIME STEPS = 7000
INFORMATION ABOUT SOLVER = YES
MASS-BALANCE = YES
DIFFUSION OF VELOCITY = YES
/

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/ INITIAL CONDITIONS
/

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ORIGINAL DATE OF TIME = 2016;02;03
INITIAL CONDITIONS = 'CONSTANT ELEVATION'
INITIAL ELEVATION = 30.45
/
/

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/ BOUNDARY CONDITIONS
/

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OPTION FOR LIQUID BOUNDARIES =1;1
PRESCRIBED FLOWRATES = 0.9;0.0
PRESCRIBED ELEVATIONS = 0.0;0.0
VELOCITY PROFILES = 4
/
LAW OF BOTTOM FRICTION = 3
FRICTION COEFFICIENT = 70
/
EQUATIONS = 'SAINT-VENANT EF'
OPTION FOR THE DIFFUSION OF VELOCITIES = 2
TYPE OF ADVECTION = 2;2
VELOCITY DIFFUSIVITY = 1.E-6
DISCRETIZATIONS IN SPACE = 11;11
SOLVER ACCURACY = 1.E-4
SOLVER = 3
DESIRED COURANT NUMBER = 0.8
C-U PRECONDITIONING =YES

FREE SURFACE GRADIENT COMPATIBILITY = 0.9

Many thanks in advance,
Regards,
Gashin

Hello

Your questions need a entire course on hydraulics and mathematical behaviour of hyperbolic conservation laws.
You need to remember that boundary conditions depend tightly to the flow regime. If your prescribed condition is not well taken into account by Telemac that means that your set of boundary conditions is not well adapted to the flow regime.
Please take the time to read carefully a basic hydraulic course in order to manage boundary condition prescription with a logical way. You can find preliminary elements in the user manual of Telemac-2D.

with my best regards


Riadh