If this node is selected from the Pairs menu, choose the pair on which to apply this condition. A pair has to be created first. See
Identity, Contact, and Sector Symmetry Pairs in the
COMSOL Multiphysics Reference Manual for more details.
The vapor concentration c0, the relative humidity
ϕw,0, and the vapor mass fraction
ω0 are always defined at the boundary. They have different expressions depending on the chosen inputs.
When Specify is set to
Relative humidity, the vapor concentration
c0 is defined as
where ϕw,0 and
T0 are the prescribed relative humidity and temperature on the boundary. For
User Defined, enter values or expressions. Else, select any available input (like
Ambient temperature defined in an
Ambient Properties node under
Definitions). The vapor mass fraction is defined as
Alternatively, choose Vapor concentration in the
Specify list and set directly the
Vapor concentration c0. The relative humidity on the boundary is then deduced
Finally, choose Vapor mass fraction in the
Specify list to set directly
ω0. The vapor concentration on the boundary is then deduced
The Constraint settings can be set to
Pointwise constraints (default),
Weak constraints or
Nitsche constraints. Select
Weak constraints to replace the standard constraints with a weak implementation. The
Nitsche constraints option ensures continuity of the diffusive flux.
Physics tab with interface as
Moisture Transport in Air, or any version of the Moisture Transport interface selected:
) and select Advanced Physics Options in the Show More Options dialog. 
