Recirculation zone over airfoil in SST model
 

Hi everyone,


I've run a simulation at Re=120000 over a thick airfoil using the SST model. The solution converges and in the post I can see a re-circulation zone towards the trailing edge. I was wondering whether this is due to a turbulent boundary layer separation or laminar. Does the plain SST (no transition) mean the entire foil has undergone a turbulent boundary layer and its separation in this case?

Regards,
Nick

Hi I think you should take a look at the following forum thread, similar issue has been discussed in detail there -
http://www.cfd-online.com/Forums/mai...-airfoils.html

If the transition model is not enabled than the turbulence model assumes the flow is turbulent everywhere.

So if you see a recirc using this model then it is a "normal" separation, not a laminar separation bubble.

Thanks Glenn. Just to clarify. So you mean it's the turbulent boundary layer that has separated ?

If you have not enabled turbulence transition model then it is using a fully turbulent model and boundary conditions everywhere. But if there is significant laminar flow about then the simulation will be inaccurate and the results rubbish.

I see. Thanks. Do you know of any resources that I can use to learn about cfx transition modelling? I need to learn about it as soon as possible.

The references listed in the documentation are the main ones. From time to time ANSYS also runs Advanced turbulence modelling courses and these go into the transition model in detail.

Much appreciated.