[letoppina]

Hello,

I am trying to simulate a tube (solid region) in which a fluid is flowing inside (fluid region). The fluid enters the tube at the inlet, flows through the tube, reaches the outlet of the tube, and comes back in a sinusoidal fashion. So it means that once the fluid enters the tube, it remains inside and it moves back and forth. It interacts with the tube walls (which are heated) so the fluid will heat up as well and increase its temperature.

Given that the fluid has a certain inlet temperature and inlet velocity, how should it be the boundary condition at the outlet?

Thank you in advance for your help!