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fakir November 23, 2006 03:23

Free Surface Modelling (sloshing)

I am after some advice on modeling free surface flow, specifically in regards to sloshing in fuel tanks.

There is a sample video on the CFX site ( showing a free-surface model, so obviously this is possible.

How does one get such high resolution? Is it just a matter of a really fine grid, and small timestep?

Currently I have a model set up, that I can apply one of six degrees of freedom too (x,y,z,yaw,pitch,roll). I use a co-ordinate frame that rotates with the tank (this was done by applying a transformation to gravity in each term, and adding a momentum source for both rotational and translational)

However when I run my simulations there is a 'mist' at the interface. Using a isosurface with VOF = 0.5, it is very bumpy, and doesn't quite seem to match up with theory.

Additionally, how do you set it up to view the entire fluid like on the CFX page? If that is an isovolume with VOF = 1, I would be interested to know how to fully resolve the air/fluid boundary.

Finally, is there any general advice for free surface modeling? (beyond the general advice for free surface modeling given in the manual/help)

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