Coupling of shallow water and circulation models for prediction of multiphysics coastal flows: Method, implementation, and experiment

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Coastal flows involve different phenomena occurring at a vast range of spatial and temporal scales, and it is now becoming necessary to synchronously simulate them, especially those in nearshore processes. This paper targets an accurate as well as simultaneous prediction of multiphysics phenomena, such as surge bores and current circulations that are distinct from each other and require different modeling methods, at high resolution and affordable computing expense. We propose a framework to predict multiphysics coastal processes by integrating existing shallow water models (SWMs) with circulation models (CMs). In particular, an unstructured mesh, Godunov-type SWM is coupled with the unstructured grid Finite Volume Coastal Ocean Model (FVCOM). The coupling is made in two-way and realized using a domain decomposition method implemented with overlapping meshes and the Schwarz alternative iteration. In order to demonstrate its feasibility and performance, the hybrid system is systematically tested in flows with tides, surge bores, and vortices, and then it is applied to coastal circulation and flooding problems. The numerical experiments indicate that the coupling system performs well in capturing different physical phenomena. Furthermore, the system may reduce computational load substantially while it maintains solution accuracy.