Cosqueric Nicolas   3rd year cfd student


 
 

MASTERING INDUSTRIAL CODES AND PARALELISM


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SUMMARY
 

1.    Presentation of the task
2.    Presentation of Telemac modelling system (version 4)
3.    Computation of a hydrodynamic problem with Telemac 2d
4.    Installation of Telemac version 5
5.    Conclusion
 

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Presentation of the task


        The purpose of this task can be divided in two parts. On the one hand, the first objective is to provide to hydraulics students the main basis in order to achieve an hydrodynamic computation with Telemac2d. On the other hand, the installation of the new version of telemac modelling system (version 5) was tested. The product of this task is a manual which explain how to carries out a computation with Telemac 2d, creates the computational grid with MATISSE and analyses the result with RUBENS
 

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Presentation of Telemac modeling structure

        introduction

        Telemac modelling system is composed of several procedures (matisse, telemac2d, artemis...) which allow to carry out computation in various fields such as hydrodynamic computation, wave propagation, bed load transport ...
The numerical method for all the procedures is based on a finite element procedure.
This code has been developing by LNHE (National Laboratory of Hydraulics and Environment), a service of EDF-DER, which is currently located in CHATOU, France (78).
This code is distributed by the company SOGREAH.
 

       Telemac structure

        In order to understand the process of a computation, the following scheme describes telemac modeling system environment
 



 


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Computation of a hydrodynamic problem with Telemac 2d


        Telemac2d solve the equations of Barré de St Venant.The main results are water height and mean velocity in vertical direction on a point of the computational grid.
        At first, Telemac modelling system is difficult to use because some stages of the computation are complex. Therefore, a simple computation was achieved on a simple case : a rivers section. A short description of the computation will be give in this part.

        1. Load Telemac environment.

        Currently, only the 4 version of Telemac is available at the ENSEEIHT. This version runs only on Windows stations. ( see next part for the use on unix or sun machines)
In order to run telemac, you have to load the file telenv.bat, open a dos control window, and execute this file. It is not really friendly therefore the installation of the 5 version on Linux or Sun machines could be effective.

        2. creation of the mesh.

        First, you must have a bottom file, which is composed of three lines : the x and y coordinates and the deep. This file can be create with SINUSX (digitalisation of a map)
This file must have the extension .sx
        Then you can run matisse. Matisse allows to create the computational grid but you can find another mesh editor. The use of matisse is quite complex at the beginning. It is based on a triangularization of the bottom points after the definition of a contour which is included in the bottom points domain. Moreover, matisse allows to create the boundary condition, for example imposed height, imposed flow...

        After the process with matisse, 2 files have been created : the geometry file and the boundary condition file. This files must be provided in a specific file for the computation of telemac 2d.

        3. The hydrodynamic simulation

        To carry out this computation, you have to provide 5 files :

- The geometry file
- The boundary conditions file
- The steering file
- The fortran file
- The results file

        The first and second file are create with matisse. The steering file is a text file where you give all the information which are necessary for the computation, that is to say the name of the five previous files, the numerical parameters and the physical parameters. It is a list of Keywords.
        The fortran file allow to fix the size of the table for the computation. This file allows to manage the memory.
        The results file is just the name of the file where the results will be stored.

        4. Analyse the results with RUBENS

        RUBENS is the post processor of the telemac modelling system which allows to control the results of an hydrodynamic computation. The utilisation is quite complex at the beginnig such as MATISSE. With RUBENS, you can check the computational grid, visualise the bottom topography, the velocities or heights.

        For example, in our simple case, we can obtain these kinds of pictures :


Mesh and bottom topography :


 
 

Velocity vectors


 
 

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Installation of Telemac version 5


        The principal difference between the fourth and fifth version is the programming language : Fortran 77 for Telemac 4 and Fortran 90 for Telemac 5. A contact was made with Pierre Lang, from the SOGREAH, in order to obtain the fifth version. Then, the computer specialist of the hydraulic department, Alexei Stoukov, tried to install the fifth version on Linux Machines but there was lots of problems uring the installation and at this time , 10/12/2001, this version is not still available but it will be in a near future.
 

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Conclusion


 


        During this task, I have learnt a new industrial code which is interesting for my personal interrest because I would work in hydraulics fields, such as fluvial or maritime problems. I have tried to write a friendly manual which allow to someone who never use telemac to realise a simple computation. I think that the installation of the fifth version on Linux will be great for the former students of  computational fluid mechanics and water science and environment option because the current environment on windows machines is quite arduous.
 

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