[morvinn]

A wall has been placed at portion(s) of an OUTLET boundary condition (at 97.5% of the faces, 97.1% of the area) to prevent fluid from flowing into the domain.The boundary condition name is: R2 Outlet The fluid name is: Fluid 1.If this situation persists, consider switching to an Opening type boundary condition instead.

how can ı solve that problem. please can someone explain ?

[ghorrocks]

FAQ: https://www.cfd-online.com/Wiki/Ansy...f_an_OUTLET.22

[morvinn]

still ı could not solve that problem. please give more detail for solve. you gave link but ı didnt undestand

[ghorrocks]

The FAQ looks pretty clear to me:

This message appears whenever backflow would occur at a pressure outlet boundary condition. This type of boundary condition cannot handle backflow into the computational domain.

If the warning message disappears before obtaining the final solution, the results are still valid. If the warning persists, you have three options:

1. Use an opening type boundary condition like the warning message suggests. However, you have to specify the direction of the backflow at an opening. Unless you have information about the direction of the backflow, the second option involves less modeling uncertainties.

2. Move the outlet further downstream to a position where no backflow occurs.

3. If the outlet and the wall is not significantly affecting your results you can ignore it and accept the solution with the back flow warning.

If you do not understand these suggestions please tell us what you don't understand.