Use a Jump node at a boundary to define a closed-loop vector field. You can add Jump nodes to interior boundaries. It is equivalent to a jump from 0 to 1 for the Diffusion Method and to a flow inlet and a flow outlet (with constant pressure) for the Flow Method; see Inlet above for the available settings. This condition is available also for the Adaptive Method. For the Elasticity Method, the jump condition is not applicable; instead, you can add an Inlet node to an interior boundary if needed.