.. _step9_section:


STEP 9 : A 2D shock tube
========================

Now the code is OK to provide 2D results. The 2D shock tube consists in a square domain. At time t=0s, the pressure is uniform (1 bar) except in a square in the center where a higher value of the pressure is imposed. At the boundaries, wall conditions are chosen to see the pressure wave bounce off the wall.


A square of 1m*1m represents the domain, meshed with 250*250 cells, the CFL number is chosen equal to 0.45. The initial pressure field can be seen in :numref:`figure_initial2Dpressure`.

.. _figure_initial2Dpressure:

.. figure:: ./_static/chapitre6_img/initial2Dpressure.png
    :scale: 75%
    :align: center

    : 2D shock tube: initial pressure field (high pressure = 5 bar, low pressure =1 bar). 


The results are plotted after a 500 timesteps run. The norm of the velocity field is presented in :numref:`figure_velocityNormFinal`. One can observe a symmetrical bounce of the flow on the walls



.. _figure_velocityNormFinal:

.. figure:: ./_static/chapitre6_img/velocityNormFinal.png
    :scale: 75%
    :align: center

    : 2D shock tube: Norm of the velocity after 500 iterations.