The Flow Continuity condition is suitable for pairs where the boundaries match; it prescribes that the flow field is continuous across the pair.

The parts of the boundary where a source boundary lacks a corresponding destination boundary and vice versa will get conditions from other boundary conditions under the physics interface acting as fallback boundary conditions on the nonoverlapping parts. By default, the Wall node is used as fallback unless another feature has been selected for the boundary.

The Wall fallback condition is incompatible with the Low Re wall treatment for the k-ω, SST and Low Reynolds number k-ε turbulence models when the overlapping parts of the pair changes with time. For nonchanging overlaps it can be made compatible by selecting Nonpair region from Allowed region under Applicable Pair Region in the Settings window for the Wall feature.

When the condition is set for pairs adjacent to domains with different porosity εp, it imposes conditions identical to the Porous Interface feature, which is designed to properly account for a sudden jump in porosity. See the section Porous Interface above for further details (note that the Flow Continuity does not account for the density-jump corrections),