Interface Conditions

Monophasic Embedded Condition

Type: PenguinBCs.Robin(α, β, g)

Discrete form (per interface DOF):

\[\beta q + \alpha u_\gamma = g.\]

q is represented by operator blocks coupled to u_ω and u_γ.

Diphasic Interface Conditions

Container: InterfaceConditions(; scalar=..., flux=...)

Scalar-like row

• ScalarJump(α₁, α₂, g)
• RobinJump(α, β, g)

Flux-like row

• FluxJump(β₁, β₂, g)
• RobinJump(α, β, g) (when used in the flux slot)

Rows map to unknown blocks as:

• γ1 row: scalar-like relation,
• γ2 row: flux-like relation.

Sampling Convention

All interface coefficients/data are sampled at C_γ:

• fixed models: capacity C_γ,
• moving models: slab-reduced C_γ.

This convention is preserved for both BE and CN/generic θ.

Practical Advice

• If only one relation is needed, set the other component to nothing.
• For no embedded interface, pass bc_interface=nothing (mono) or ic=nothing (diph).