Semi-implicit non-hydrostatic model for 2D nonlinear wave interaction with a floating/suspended structure

A non-hydrostatic model is developed to simulate two-dimensional (2D) nonlinear wave interaction with a fixed floating/suspended structure. The immersed boundary method is incorporated in the model to address arbitrary body surfaces. The model employs a semi-implicit, fractional step algorithm to solve the Reynolds-averaged Navier-Stokes (RANS) equations based on a grid system, which is built from a horizontal rectangular grid by adding dozens of horizontal layers. The horizontal layers are distributed following a general boundary-fitted vertical coordinate system. This grid system may overcome the lack of flexibility of other boundary-fitted coordinate systems (e.g., the σ-coordinate system). The model is validated by using three test cases, namely, a solitary wave interacting with a floating rectangular obstacle, a solitary wave incident on a suspended horizontal plate and a solitary wave incident on a coastal-bridge deck with girders. Numerical results of the free surface elevation and wave force exerted on each structure are compared with the results of other models or experimental data. Generally, good agreements are obtained, demonstrating the proposed model's capability to resolve nonlinear wave interactions with floating/suspended structures. The velocity fields around the structures are also presented and discussed.