Learning Forum

[Bill Hsu]

Hello everyone,

I'm trying to simulate the air conditioner and the air purifier to dilute the particle in the indoor space, but my flow direction arrow (the red one) of the air purifier outlet was not what I expected, how can I reverse the flow direction arrow in the Fluent? My boundary condition of air purifier outlet need to set as outflow condition, so I cannot set the property such as velocity to a negative value.

[CFD_Friend]

Hi 

Can you check out this post

How to Change the Direction of the Normal Vector of the Internal Face - Ansys Knowledge

[Bill Hsu]

Thanks for your suggestion! I'll try to change the direction of the normal vector according to your information.

[CFD_Friend]

Hi Bill,

The vector plot at the outlet seems like they are pointing in the right direction. Can you reduce the scale of the vectors and confirm if it's pointing right? You can reduce the scale by going to the vector plot options. 

I would suggest using the Presure Outlet boundary condition rather than Outflow.

[Bill Hsu]

Hi, thanks for your reply! 

1. About the vector pointing, you are right! It seems no problem with the direction.
2. The reason why I use the outflow boundary condition is most of the journal papers in my research field (particle removal and suspension in indoor space) use the Neumann boundary condition, which ensures the mass flow rate out of the domain the same as the mass flow rate into the domain, and I search the Neumann boundary condition on the internet, people said that the outflow boundary condition could satisfy the Neumann boundary condition, did I wrong with these concepts? or the pressure boundary condition can satisfy the Neumann boundary condition as well?