[Sina R]

Hello
I have a problem with an air flow inside a pipe, the continuity residual does not drop below e-01.
Here are the flow properties: Inlet velocity of 40 m/s and the pressure difference between the inlet and the outlet is 0.3bars.
The piping has a 90 degree elbow in it going upwards.
The length of the pipes connected are 1 and 1.5 meters.
I'm currently using k-epsilon RNG model for the viscosity.
I don't know where the problem is, I've tried two different sets of meshing too. Could you please guide me on a good mesh size (or the number of divisions and inflation) and the suitable "methods" options?
Many thanks in advance

[xisluke]

First of all, residuals are not the only parameters you have to look at when you need to check for convergence; I suggest you to look for physical variables at the inlet/outlet of your domain instead. Generally speaking, in your case residuals are probably affected mostly by the turbulence model, mesh and URFs. If you want to use a k-epsilon model, you can try to adopt the Realizable, with Scalable wall-functions, I think it will be probably more stable than RNG.