REEF3D::NHFLOW—A high-performance non-hydrostatic solver for coastal wave propagation

In this paper the new three-dimensional non-hydrostatic wave model NHFLOW is presented. It solves the non-hydrostatic Euler equations on a $\sigma$-coordinate grid, which follows the free surface and bottom topography, allowing for grid refinement near the water surface. The governing equations are treated with a Godunov-type scheme. A pressure correction algorithm is implemented, which results in excellent dispersion properties. Together, this delivers a unique combination of shock-capturing properties and dispersive wave modeling capabilities. The structure of the coefficient matrix of the Poisson equation is simplified through a deferred correction approach, increasing the iterative solver’s performance significantly. In order to model propagating waves with a high level of accuracy, the numerical fluxes are reconstructed with the fifth-order WENO scheme. Developed within the open-source hydrodynamic framework REEF3D, the new model is fully parallelized and utilizes the domain decomposition strategy with MPI communication between processors. This paper showcases the capabilities of this new and efficient non-hydrostatic model through verification and validation with a range of laboratory and real-world wave propagation cases.