Does the wall BC set k & e to zero?

May 8, 2006, 06:30

Hi,all!

I use the ske model and set the BC as "WALL" for some solid boundarys. But after caculation I ploted turbulence kinetic energy(k) along these "walls" and found them not equal to 0. Why???

I tried adding some source terms to the momentum equations, but the caculations diverged soon. I checked the values of k and found them quite large somewhere on the wall. I think this resulted in the divergence.

Can anyone tell me how fluent set the "WALL" BC? If I change the boundary condition "wall" to "velocity inlet" and set velocity,k and e to 0, is there any problem?

Any help will be very appreciated!

May 8, 2006, 13:39

The default boundary condition for a wall is no-slip, so the immediately adjacent velocity is 0. Maybe if you set the walls to be slip walls (in the wall boundary condition panel) you would get nonzero k and e.

May 8, 2006, 22:53

The problem is that I want k and e on the wall to be equal to ZERO but FLUENT actually don't set them to zeros in the default WALL boundary condition.

Marta · December 10, 2010, 12:49

Hi guys!
I am trying to create a boundary condition in Fluent similar to the wall+source which can be found in CFX.
Do you know if it's possible for me to use any kind of udf to do this?

In particular what I would like to do is to add a mass flow rate source, instead of using the mass flow inlet boundary.
This is because i need to perform some other operations which are only allowed on walls.

Thanks a lot in advance!

Marta

May 8, 2006, 06:30	Does the wall BC set k & e to zero?	#1
Lucy Guest Posts: n/a	Hi,all! I use the ske model and set the BC as "WALL" for some solid boundarys. But after caculation I ploted turbulence kinetic energy(k) along these "walls" and found them not equal to 0. Why??? I tried adding some source terms to the momentum equations, but the caculations diverged soon. I checked the values of k and found them quite large somewhere on the wall. I think this resulted in the divergence. Can anyone tell me how fluent set the "WALL" BC? If I change the boundary condition "wall" to "velocity inlet" and set velocity,k and e to 0, is there any problem? Any help will be very appreciated!

May 8, 2006, 13:39	Re: Does the wall BC set k & e to zero?	#2
Evan Rosenbaum Guest Posts: n/a	The default boundary condition for a wall is no-slip, so the immediately adjacent velocity is 0. Maybe if you set the walls to be slip walls (in the wall boundary condition panel) you would get nonzero k and e.

May 8, 2006, 22:53	Re: Does the wall BC set k & e to zero?	#3
Lucy Guest Posts: n/a	The problem is that I want k and e on the wall to be equal to ZERO but FLUENT actually don't set them to zeros in the default WALL boundary condition.

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December 10, 2010, 12:49		#4
Marta Member Marta Lazzarin Join Date: Jun 2009 Location: Italy Posts: 71 Rep Power: 17	Hi guys! I am trying to create a boundary condition in Fluent similar to the wall+source which can be found in CFX. Do you know if it's possible for me to use any kind of udf to do this? In particular what I would like to do is to add a mass flow rate source, instead of using the mass flow inlet boundary. This is because i need to perform some other operations which are only allowed on walls. Thanks a lot in advance! Marta