Quicker convergence with clear separation? (example with Karman vortex sheet)
 

Hi all,

I wasn't sure where to put this, so I put it here as I'm working with OpenFOAM myself.

I'm working through some tutorials and making my own adjustments to hopefully gaining a better understanding. I was doing an example of external flow around a cylinder using icoFoam, developing a Karman Vortex sheet. I wanted to understand better how these fluctiations developed, so I took out part of the cylinder in the wake, keeping all the setup the same.

I plotted the results in the same ParaView window, resulting in the following .gif (sorry, tried to compress, currently still 8MB..). Bottom one is obviously the normal cylinder, top one has a chunk missing in the top right.

http://i.imgur.com/3aecCh5.gif

The way I see it, the fluctuations are consistent much quicker in the top case. Is it safe/correct to see that the top case converged much quicker? Is this due to the increased adverse pressure gradient triggering separation more quickly, is it due to an error in my setup or am I missing the point completely?

Cheers,

Bruno

*edit*
I feel like maybe this should've gone here? http://www.cfd-online.com/Forums/openfoam-solving/
If a mod agrees and could move it, thanks.