An Open Boundary Condition for Application in Numerical Coastal Models

Open boundaries (OBs) are usually unavoidable in numerical coastal circulation simulations. At OBs, appropriate open boundary conditions (OBCs) are required and a good OBC should be able to let outgoing waves freely pass to the exterior of a computational domain without creating reflections at the OBs. In the present study, a methodology has been developed to predict two parameters, phase speed c and decay time T , in a standard OBC formulation, so that the OBC is significantly improved compared to commonly used existing OBCs with specified c and T . For the conditions where wave period is unknown, the OBC with approximated c and T may be applied and a test reveals that this OBC is able to yield good results in typical coastal flow conditions. In addition, a Swing-Door Boundary Condition (SDBC) is proposed and tested for application at an offshore open boundary where both incoming and outgoing waves exist.