Opening BC: Normal to boundary
 

Hello all,

In a calculation, i specify the opening boundary condition because I am having problems with backflow at the outlet. There is an option set "Normal to Boundary" for the velocity direction. Everything converges well, but when I plot the velocity vectors on my outlet surface I notice that they are not at all normal to the boundary. Is this a bug? (using CFX 10).

Greetz,

Jan

Re: Opening BC: Normal to boundary
 

No it's not a bug. On an opening boundary condition, the "Normal to Boundary" part refers to the flow entering the domain only. The flow exiting the domain can be in any direction.

Re: Opening BC: Normal to boundary
 

if u want that velocity vector are normal from your outlet, you could force it by redefining your BC with a velocity profil. bye alex

Re: Opening BC: Normal to boundary
 

I think forcing the outlet condition will not solve the problem. Better try to extend the outlet geometry longer thus u can avoid backflow at the outlet.

Viele Gruß scrijnczw