Reference pressure for convergence
 

Hi,

I'm wondering, in order to make the simulation converge, should I set the reference pressure as precise as possible? Is it possible to set different reference pressure to different fluid domain? Thanks!

No, the reference pressure must be across all domains.

It is not normal to need to precisely set the reference pressure. Near enough is good enough. If small changes in the reference pressure makes a difference then your simulation is not well set up.

Refrence pressure is one for entire simulation and is same for all domain. Whatever last change you make to refrence pressure in any domain, gets applied to all domain.
As far as my understanding goes there is no precise value for reference pressure and it can take various values. Aim is to get rid of round off error when absolute pressure is quite large compared to pressure changes in domain. Imp thing is to set Relative pressure in BC’s relative to this reference pressure. I think that its value should not affect convergence or accuracy but if not set properly it can lead to solver failure.