swirl flow, B.C. for exit?
 

Dear colleagues.

Could you answer some questions about computing of swirl flow?

I have been computing flow in cylindrical tube with swirl. Input data for my problem is following:

Diameter of tube - 0.06 m. Length - 0.6 m

B.C. for exit: Axial velocity - 2 m/s Swirl velocity - 1.5 m/s Radsial velocity - 0 m/s

Fluid - water Re=120000 Swirl number = 0.5 Solver model-2d axisymmetric

I have problem with outlet boundary condition. I used two types of exit conditions: outflow and pressure-outlet( p=const) And obtained two different results.

What type of conditions is correct?

Re: swirl flow, B.C. for exit?
 

Hi victor,

Applying "Outflow" bc means the flow at the outlet is fully developed. Using this for a situation where flow is not developed can give misleading results.

In this situation pressure outlet is the best one. Once the velocity is specified, its just a difference of pressure that matters. So specify 0 outlet pressure.

Regards

Bipin