Grid configuration

    We first choose to study the Rayleigh-Benard instabilities in a two dimension case. Practically, it is the kind of flow that we could observe in a fluid between two horizontal flat walls of large dimension, compared to the fluid thickness.
The dimensions of the simulated zone are 2 cm in the horizontal direction (x) and 1 cm in the vertical dimension (y).

The grid  is composed of 5000 squared cells (50x100).

The boundaries conditions are:
    - symmetry on the vertical boundaries
    - Temperature given on the wall

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Conditions of the Calculation

    In all the cases we studied, the Rayleigh number stay close enough to the critical Rayleigh number to stay in laminar flow. That is why we always choose the laminar model.
 
Define=>Models=>Viscous... 

For the buyancy resulting from the difference of density, we have to change one parameter in the Materials menu. (Define=>Materials...).

We change the density from constant to Boussinesq.




A new field appears under the viscosity, it is the thermal expansion coefficient. It has to be filled. We have chosen the value of 0.00012.






All others parameters where not modified.