Abstract
This paper aims to present the extension of the non-hydrostatic wave-flow model SWASH with the covolume method to build discretization schemes on unstructured triangular grids. Central to this method that is free of spurious pressure modes, is the use of dual pairs of meshes that are mutually orthogonal, such as the Delaunay-Voronoi mesh systems. The approximants sought are the components of the flow velocity vector normal to the cell faces of the primal mesh. In addition to the covolume approach, a novel upwind difference scheme for the horizontal advection terms in the momentum equation is proposed. This scheme obeys the Rankine-Hugoniot jump relations and prevents the odd-even decoupling of the velocity field accordingly. Moreover, cases with flow discontinuities, such as steady bores and broken waves, are properly treated. In spite of the low-order accuracy of the proposed method, unstructured meshes easily allow for local refinement in a way that retains the desired accuracy. The unstructured-grid version of SWASH is applicable to a wide range of 2DH wave-flow problems to investigate the nonlinear dynamics of free surface waves over varying bathymetries. Its efficiency and robustness is tested on a number of these problems employing unstructured triangular meshes.
Highlights
A commonly encountered coastal engineering application involves the simulation of dispersive waves in coastal waters
This paper aims to present the extension of the non-hydrostatic wave-flow model SWASH with the covolume method to build discretization schemes on unstructured triangular grids
The unstructured-grid version of SWASH is applicable to a wide range of 2DH wave-flow problems to investigate the nonlinear dynamics of free surface waves over varying bathymetries
Summary
We present results for four test cases with an increasing degree of difficulty in the unstructured mesh configuration. The objective is to assess the ability of the present unstructured staggered mesh approach to reproduce these wave processes with an emphasis on predictive accuracy. For stability reasons the time step is restricted to comply with the CFL condition that depends on the wave celerity. This condition is given by t ghf + |u f |. Boundary conditions considered here pertain mainly to the generation of incident free short waves and bound infragravity waves. They are imposed as weakly reflective at the offshore boundary. The staggered mesh method described in this paper will soon be released in a future version of SWASH (http: //swash.sourceforge.net), though the source code and a detailed description of the implementation can be obtained from the author upon request
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