The Wetted Wall node is the default boundary condition representing wetted walls. Along a wetted wall the contact angle for the fluid, θw, is specified, and across it, the mass flow is zero. This is prescribed by

The contact angle θw can be defined directly or from Young’s equation, which considers the components of the forces in the plane of the surface:

where γs1 is the surface energy density on the fluid 1 — solid (wall) interface and γs2 is the surface energy density on the fluid 2 — solid (wall) interface.

Select an option from the Specify contact angle list — Directly (the default) or Through Young’s equation. For Directly enter a value or expression for the Contact angle θw (SI unit: rad). The default value is π/2 radians. For Through Young’s equation enter values or expressions for Phase 1-Solid surface energy density γs1 (SI unit: J/m2) and Phase 2-Solid surface energy density γs2 (SI unit: J/m2).