REEF3D::FNPF—A Flexible Fully Nonlinear Potential Flow Solver

Abstract

In situations where the calculation of ocean wave propagation and impact on structures are required, fast numerical solvers are desired in order to find relevant wave events. Computational fluid dynamics (CFD)-based numerical wave tanks (NWTs) emphasize on the hydrodynamic details such as fluid–structure interaction, which make them less ideal for the event identification due to the large computational resources involved. Therefore, a computationally efficient numerical wave model is needed to identify the events both for offshore deep-water wave fields and coastal wave fields where the bathymetry and coastline variations have strong impact on wave propagation. In the current paper, a new numerical wave model is represented that solves the Laplace equation for the flow potential and the nonlinear kinematic and dynamics free surface boundary conditions. This approach requires reduced computational resources compared to CFD-based NWTs. The resulting fully nonlinear potential flow solver REEF3D::FNPF uses a σ-coordinate grid for the computations. This allows the grid to follow the irregular bottom variation with great flexibility. The free surface boundary conditions are discretized using fifth-order weighted essentially non-oscillatory (WENO) finite difference methods and the third-order total variation diminishing (TVD) Runge–Kutta scheme for time stepping. The Laplace equation for the potential is solved with Hypre’s stabilized bi-conjugated gradient solver preconditioned with geometric multi-grid. REEF3D::FNPF is fully parallelized following the domain decomposition strategy and the message passing interface (MPI) communication protocol. The numerical results agree well with the experimental measurements in all tested cases and the model proves to be efficient and accurate for both offshore and coastal conditions.

Intercomparison of Three Open-Source Numerical Flumes for the Surface Dynamics of Steep Focused Wave Groups

“…Also, the complication of solving for two-phase fluid flows in OpenFOAM may be a source of error that should not be factored out. To confirm these findings and be able to identify credibly the sources of the errors, other suitable solvers can be used that employ similar equations and modelling approaches as these of the present work [66,67].…”

A Comparison of Different Wave Modelling Techniques in An Open-Source Hydrodynamic Framework

“…From wave gauges 1 to 4, the x-coordinates are x = 19.8, 20.8, 21.8 and 22.1 m. The simulations are computed with four 2.7 GHz Intel Xeon E5 cores on Mac Pro for REEF3D::FNPF and REEF3D::SFLOW and 128 2.1 GHz Intel E5-2683v4 cores on the supercomputer Fram. The grid convergence study for the three models REEF3D::CFD, REEF3D::SFLOW and REEF3D::FNPF were reported respectively by Bihs et al [1], Wang et al [47] and Bihs et al [51]. As a result, the dx = 0.005 m, dx = 0.005 m and dx = 0.005 m are used in the REEF3D::CFD, REEF3D::SFLOW and REEF3D::FNPF simulations respectively.…”

Validation of Numerical Wave Tank Simulations Using Reef3d With Jonswap Spectra in Intermediate Water Depth

“…The new numerical wave model FNPF of REEF3D solves the Laplace equation for the flow potential and the nonlinear kinematic and dynamics free surface boundary conditions [15]. Very promising results in the reproduction of experimental regular and bi-chromatics wave with constant water depth as well as with complex bottom topology have been presented with the open-source hydrodynamic model REEF3D::FNPF in [16] and [17]. This approach requires reduced computational resources compared to CFD based NWTs.…”