Transitionmodeling
 

Hi,

I'm modeling transition through free convection around a horizontal cylinder. When using the SST k-omega model without a roughness height I get a flow that is laminar, however when putting the roughness height to a value around 2.5 cm I get a turbulent transition.

My y+ values are below 1 and the first cell height is less than 1 mm. The manual states that the roughness height shouldn't be set to a value higher than half the height of the first cell, which I have done.

Can I apply surface roughness with such a small y+ and thin boundary layer? Would be glad for any hints or suggestion concerning transition modeling!