The observation of instability with a numerical study is very hard. In order
to reach this objective, the computation needs to be the most precise as
possible.

The consequence is that the time of calculation could be very long. Moreover,
it's not really interesting.

For these reason we have looked in the help of FLUENT for a way to make a
batch calculation.

This possibility exists in FLUENT, it just need an instructions file
and it returns a file which contains all what it do.
The syntax is :

fluent 2d -g <commande>& batch.out&

An example of ``commande'' file is :

rc def.cas rd def.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def10.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def20.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def30.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def40.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def50.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def60.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def70.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def80.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def90.dat solve/set/time-step 0.01 solve/set/reporting-interval 20 solve/dual-time-iterate 10 it 100 wd def100.dat exit

This ``commande'' file begins with the instructions for read a FLUENT case, then a data file. After that it executes the computation and after time steps it saves the data in a file. With this file it does that times.

With this batch treatment of the computations, we have to be more concentrated on the case that on the time of the computation. It was very pleasant.