[FMDenaro]

In my opinion, the grid is extended enough from the cylinder, perhaps I don't understand the requirement to use an O-grid ...
First, the instability should appear also for laminar flows, therefore I would try the solver without any tubrulence modelling, then I see only 600 time-steps that can be not sufficient to develop instability. An acceleration of the onset of the instability can be obtained by prescribing small fluctuations in the initial condition.
Finally, owing to the particular shape of the grid, I would take attention to the outflow conditions

[arjun]

Originally Posted by RodriguezFatz

But do you think his domain looks like it is too small compared to the radius?

can't really say. Because with iNavier and old versions of fluent like fluent 6.3 i could get vortex shedding even when boundaries were close.

I was just sharing my experience with such problem how it went away. So it is worth trying. Personally I do think with finite volume codes like fluent starccm he should have got this vortex shedding without much of hassle.

[arjun]

Originally Posted by FMDenaro

In my opinion, the grid is extended enough from the cylinder, perhaps I don't understand the requirement to use an O-grid ...
First, the instability should appear also for laminar flows, therefore I would try the solver without any tubrulence modelling, then I see only 600 time-steps that can be not sufficient to develop instability. An acceleration of the onset of the instability can be obtained by prescribing small fluctuations in the initial condition.
Finally, owing to the particular shape of the grid, I would take attention to the outflow conditions

that may very well be the issue here. It usually requires much larger number of steps to get.