A horizontally curvilinear non-hydrostatic model for simulating nonlinear wave motion in curved boundaries

Abstract

SUMMARY A horizontally curvilinear non-hydrostatic free surface model that embeds the second-order projection method, the so-called θ scheme, in fractional time stepping is developed to simulate nonlinear wave motion in curved boundaries. The model solves the unsteady, Navier–Stokes equations in a three-dimensional curvilinear domain by incorporating the kinematic free surface boundary condition with a top-layer boundary condition, which has been developed to improve the numerical accuracy and efficiency of the non-hydrostatic model in the standard staggered grid layout. The second-order Adams–Bashforth scheme with the third-order spatial upwind method is implemented in discretizing advection terms. Numerical accuracy in terms of nonlinear phase speed and amplitude is verified against the nonlinear Stokes wave theory over varying wave steepness in a two-dimensional numerical wave tank. The model is then applied to investigate the nonlinear wave characteristics in the presence of dispersion caused by reflection and diffraction in a semicircular channel. The model results agree quantitatively with superimposed analytical solutions. Finally, the model is applied to simulate nonlinear wave run-ups caused by wave-body interaction around a bottom-mounted cylinder. The numerical results exhibit good agreement with experimental data and the second-order diffraction theory. Overall, it is shown that the developed model, with only three vertical layers, is capable of accurately simulating nonlinear waves interacting within curved boundaries. Copyright © 2011 John Wiley & Sons, Ltd.