In the example about Domain Decomposition, for the “Schwarz non overlapping Scheme”, lambda is actualized as: lambda = lambda - (u-U)/2
What I don’t really understand is that U is a fem variable defined inside a mostly circular domain cut by a inclined line, and u is a fem variable defined inside rectangular domain with an inclined side that coincides with that one of the circular domain.
So, what does U-u mean? Those variables are defined over different domains that have a common boundary. So, in general, what do operate mixing variables of different domains mean?