Non-Conformal Coupling: Connecting CFD regions through topologically unmatching interfaces

We implemented in the HELYX CFD software an efficient and flux conservative approach to couple unconnected regions through non-conformal interfaces. The mesh connectivity is achieved by projecting one side of a boundary patch onto its neighbour. The intersection between patches creates new faces that are incorporated into the finite-volume mesh. These faces are created identically on both sides of the coupling, becoming equivalent to internal faces within the mesh. As a consequence, the main benefits of the finite-volume method, i.e. conservation and accuracy, are not undermined by the strategy. A comparison to the AMI approach shows improved accuracy, boundedness and conservation, at the same computational cost for static coupling, and a small increase in runtimes for sliding interfaces.