Telemac 2D


Physical background
Numerical background
Classical errors

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1. Physical Background
Telemac 2d solve the equations of Barré de Saint-Venant in the two horizontal space co-ordinates U(x,y). The main results are the mean vertical velocity and water height.
The following phenomenons are taking into account :
- Propagation of long waves with accounting of non-linear effects.
- Bottom friction
- Coriolis forces
- Wind and atmospheric pressure
- Turbulence
- Influence of horizontal gradient of temperature or ... on the density
- follow trace
- Singularity treatment such as :
The model is the following :



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2. Numerical computation
2.1 Input / Output
There is at least 4 files to provide in order to carry out a computation with Telemac-2D. Indeed, if you want to continue a previous computation, you have to provide the previous result file.
2.1 Input
2.1.1 The geometry file
It contains the co-ordinates of the the computational grid, create by MATISSE, or an another mesh generator.
1.2 The parameters file
It is a text file which contains all the key-words which are necesary for the computation such as initial condition, numerical parameters or physical parameters.

Example of a parameter file


1.3 The Fortran file

It contains all the subroutine of telemac which have been modified by the user. Moreover, it contains the principal program of Telemac. The main function of this program is to fix the language (french or english), and to fix the memory space by dimension the table A (real) and IA (integer). To fix the memory, you must know the number of points in the grid.

1.4 The boudary conditions file

It contains the definition of the boundary (fixed flow, fixed height, wall...). This file is created by the mesh generator.

For each point of the grid, there are the following values (for a cartesian grid) :

LIHBOR Boundary type (integer) 
LIUBOR Boundary type (integer)
LIVBOR Boundary type (integer)
LITBOR Boundary type (integer)
HBOR Imposed height when LIHBOR = 5
UBOR Imposed velocity U when LIUBOR=6
VBOR Imposed velocity V when LIVBOR=6
AUBOR Friction coefficient at the boundary when LIUBOR orLIVBOR = 2
TBOR Imposed value of the when LITBOR = 5
ATBOR flux coefficient
BTBOR flux coefficient
N global number
I co-ordinate number
J co-ordinate number

Exemple :

2. Output
2.1 The listing file
It contains all the information concerning the computation
2.2 The results file
It contains the results of the computation. It is the file which will be compute with RUBENS
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2.2 Hydrodynamic computation
2.2.1. Initial conditions
The initial conditions define the model at the time of the beginning of the computation. In the case of former computation, the initial conditions are described by the old results file.
The initial condition are fixed in the parameters file by the use of Key-words for simple case or by programming for complex case.
Key words
Initial conditions nature are fixed by the key words CONDITIONS INITIALES, which can take 5 values
COTE NULLE : Initialize the height of the free flow surface at the value 0 meter.
COTE CONSTANTE : Initialize the height of the free flow surface at the value given by the Key word 'COTE INITIALE'
HAUTEUR NULLE : Initialize the water heights to 0 meters. Therefore, the domain is dry.
HAUTEUR CONSTANTE: Initialize the water heights to the value given by the key word HAUTEUR INITIALE.
Continue a computation from an old computation
The name of the result file must be the name of the previous computation.
In the initial conditions field, you have to imposed the following keywords :
SUITE DU CALCUL take the value OUI
FICHIER DU CALCUL PRECEDENT is the name of the previous computation file.

2.2.2. Boundary conditions

The type of the boundary condition is fixed by the value of LIHBOR, LIUBOR, LIVBOR, LITBOR, which can take a value from 0 to 6.

Possible choice :
Height condition
Liquid boundary with fixed height LIHBOR = 5
Liquid boundary with free height LIHBOR = 4
Liquid boundary with incident wave LIHBOR = 1
Solid frontier LIHBOR = 2
Velocity or flow conditions
Liquid boundary with fixed flow LIUBOR/LIVBOR = 5
Liquid boundary with fixed velocity LIUBOR/LIVBOR = 6
Liquid boundary with free velocity LIUBOR/LIVBOR = 4
Solid boundary with friction or LIUBOR/LIVBOR = 2
Solid boundary with 1 or 2  of the velocity null LIUBOR/LIVBOR = 0

Nevertheless, for a Telemac computation, you can fixed the conditions type in matisse which is well adapted for telemac2d


2.2.3. Prepare the computation

Now, you have to fix all the parameters in the parameter file and the name of the different file.
In the fortran file, you fix the size of the table IDIMIA and IDIMA (You have to now the number of points in the grid)

Moreover, you have to fix the parameter in the parameter file such as :

You can also choose a break criteria : Bottom friction

Telemac allows to the user to choose the formula for the bottom friction. It is defined in key-word COEFFICIENT DE FROTTEMENT which can take a value from 0 to 5.
1 Haaland
2 Chézy
3 Strickler
4 Manning
5 Nikuradse

You can also choose a modele for the turbulence with the key word MODELE DE TURBULENCE.
1 Constant viscosity
2 Elder
3 k-Epsilon
4 Smagorinski


2.2.4. Run the computation

In the dos-control window, type telemac2d Name_of_the_parameter_file. (in batch mode, type telemac2d -b Name_of_the_parameter_file

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3. Classical errors
3.1 Size of IDIMA and IDIMIA.
The computation stop if the size of these tables is too little. Therefore, be carreful and when you achieved mesh in Matisse, don't forget to note the number of grid point.
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