A robust patch coupling method for NURBS-based isogeometric analysis of non-conforming multipatch surfaces

This paper presents a simple yet flexible method for coupling non-conforming NURBS patches in isogeometric frameworks. It consists of virtually refining bordering patches to derive coupling constraints in a master-slave formulation. These constraints are then enforced via a substitution method for condensation of the slave variables, thereby reducing the model size. In the special case of hierarchical meshes, the method results in an exact connection. For an arbitrary non-conforming configuration, the master-slave formulation takes the interface constraints into account in a least-squares sense. This yields an accurate weak coupling without overconstraining the interface. The coupling relationships only depend on the mesh itself and not on any problem-dependent parameters, allowing them to be generated in a pre-processing step with very limited numerical efforts. Besides this low computational cost, the main merit of the proposed method lies in its simplicity and robustness, yielding good results for arbitrarily strongly non-conforming patch configurations. Several numerical examples are studied for different problem types requiring C0- or C1-continuity, in particular time-harmonic acoustics and (dynamic) thin plate bending. Benchmarking of the proposed approach against existing similar techniques illustrates its superior accuracy and robustness.