[zxcvasdf]

Hi
Does fluent can detect negative velocity in velocity inlet boundary condition?
It means that direction is variabe sometimes i need a reversed direction
Thanks

[LuckyTran]

You can specify an arbitrary direction vector for the velocity.

But Fluent does not do any "detection." The velocity is specified by you so I don't what you want Fluent to detect.

[bboynido]

here I attached some images that explains how to set your velocity in a readable way for FLUENT.
Before going to FLUENT, you can:
1/ create named selections for your velocity inlet and outlet using DesignModeler or Ansys meshing (the images 1/2 show how to do that using Ansys meshing) .
2/open Fluent and import your mesh (the one that you already created named selection in )
3/go to Boundary conditions, you notice that FLUENT recognize the velocity inlet as shown in image 3. Edit your velocity inlet as shown (either using magnitude and directions or components of velocity as shown in images 4 and 5 ) .

[zxcvasdf]

Thanks but there is a problem with this:
The negative direction is available just for one coordinate for example just x direction or just y direction could be negative and other must be possitive.
I mean the condition that both of them be negative how can i do this?

[bboynido]

It depends on the named selections you make, if you have two directions of velocity select two external faces (as you saw above) and set two surfaces as velocity-inlet1 and velocity-inlet2 then Fluent will recognize them both , and you can set each one of them on a negative direction(like -55,0,0 inlet1 and 0,-55,0 inlet2 for components of velocity) it will be what you are looking for since your domain is homogenous and contain the same fluid with the same properties