B.C. for an opening between inside and outside
 

Dear all,

Which boundary condition is the best for an opening between inside and outside?
Note that the air flow is possible through this opening without any limitation.

Thank you in advance.

In most cases, an opening would be a suitable choice.

It allows the flow to leave and enter the domain. An outlet would prevent the flow from entering the computational domain.

Dear Alexander Stief,
Thank you for your reply.
I searched for the B.C. type of “opening”, but I have not found that.
Could you please let me know where I could define it? Or, just leave it and it would be automatically assumed as the opening?
Best regards,
sagila

Sorry, my bad. The name "opening" only exists in CCM+.

In fluent, the "pressure outlet" corresponds to this type of boundary condition.