"boundary" vs "interface"?

I am working with biofilm and there are many documents talking about boudary conditions while others talks about interface or both of boundary and interface. So, boundary and interface are the same (in numerical analysis) or not? why and examples?

1 Answer

I'm not particularly familiar with biofilm literature. But in most computational literature, the border of the entire domain of a problem are usually referred to as the boundary. Outside of a boundary, there are no nodes, elements, or anything else under consideration.

The entire domain may also be subdivided into smaller regions. Some of these regions share edges on the boundary of the domain. However, some of these regions share borders between each other that are not boundaries of the domain. Usually these regions have different material properties or different relevant physics and may also have different meshes. The borders between any two regions in a domain are usually referred to as interfaces.

• In multiphase flow, the boundary between phases is usually referred to as an "interface" to distinguish it from the actual physical boundaries surrounding the system. Feb 16, 2014 at 3:16
• In some literatures, I found that the authors use the term "interfaces" to indicate the geometry position/properties between 2 fluids/phases/something else... However, when they need to use a boundary condition on these interfaces, they call them boundary in term "boundary condition" (not "interface condition" ^^). So, generally, 2 terms are only different about their meaning, is that right? Feb 16, 2014 at 13:53
• @PoBo: That is true. Sometimes, the interface condition is also referred to as a boundary condition. But it is a boundary condition of the subregion, as opposed to the boundary condition of the domain.
– Paul
Feb 16, 2014 at 16:46