Hi, everyone My case is that fluid flow in a channel. The wall of channel is porous media. I set the boundary type "interface" between porous media and fluid in Gambit. Meanwhile, i have a user defined scalar(UDS). The boundary condition at this interface must satisfy following condition: C1*(DS/Dn)=C2*(DS/Dn) S: user defined scalar C1:constant 1 C2:constant 2 n:the normal vector of interface

My question: How to define this kind of boundary condtion in FLUENT Thank you very much in advance.

For an interface within your domain (ie. not a wall or inlet/outlet) you will need to force the boundary condition on the UDS by one or more of the following methods:

1) define a UDS_SOURCE udf 2) define a UDS_FACE_FLUX udf 3) define a UDS_UNSTEADY udf For your condition I think you'll need to use 2) and may need to also use 1) as well. This can be tricky to work out, but its possible.

Good Luck! Greg