
Hybrid Structure-Preserving Discretisations with C1 Multi-Patch Splines.
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Various C1 multi-patch spline spaces have been developed in recent years [1]. Such spaces can lead to more accurate and efficient methods due to a decreased number of degrees of freedom. However, C1 spaces introduce basis functions supported on multiple patches. So, while there are fewer degrees of freedom in the final system, this system will be denser and more globally intertwined. Discretisations using C0 multi-patch splines, however, may be solved efficiently using hybridisation: breaking the global function spaces to per-patch spaces and re-introducing their continuity through Lagrange multipliers. The resulting matrix system can be efficiently solved using static condensation. This approach is particularly interesting in the context of structure-preserving discretisations [2], where suitable choices of finite-dimensional spaces can lead to improved accuracy and stability [3]. Building a hybrid and structure-preserving discretisation using C1 multi-patch splines can thus lead to versatile, accurate, and efficient discretisations. However, the use of C1 spaces and the role of smoothness in combination with hybridisation has only been investigated in the context of mortar methods [4]. In this work, we will provide further insights into the connection between C1 splines and hybrid structure-preserving discretisations. The Poisson problem will be used to show some examples of our method. This also allows us to highlight some similarities and differences between the C1 and C0 approaches. It also allows us to compare the continuous C1 discretisation and its hybrid counterpart in terms of accuracy and efficiency.