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The performance of interFoam (a widely used solver within OpenFOAM®) in simulating the propagation of a nonlinear (stream function solution) regular wave is investigated in this work. It is demonstrated that over time there is a tendency for surface elevations to increase, wiggles to appear in the free surface, and crest velocities to become (severely) overestimated. It is shown that increasing the temporal and spatial resolution can mitigate these undesirable effects, but that a relatively small Courant number is required and fine discretization is needed, indicating that many past simulations have not converged. It is further demonstrated that discretization schemes and solver settings (often treated as a "black box" by users) can have a major impact on the results. This impact is documented, and it is shown that obtaining a "diffusive balance" is crucial to accurately propagate a surface wave over long distances without requiring exceedingly high temporal and spatial resolutions. Finally, the new code isoAdvector is demonstrated to produce comparably accurate results to interFoam, while maintaining a sharper surface. It is hoped that the present study will raise awareness of potential shortcomings of interFoam and enable a more accurate and optimal use, in CFD simulation of free surface waves. [ABSTRACT FROM AUTHOR]

A fully coupled hydrodynamic and morphologic numerical model was utilized for the simulation of wave-plus-current scour beneath submarine pipelines. The model was based on incompressible Reynolds-averaged Navier-Stokes equations, coupled with k-ω turbulence closure, with additional bed and suspended load descriptions forming the basis for seabed morphology. The model was successfully validated against experimental measurements involving scour development and eventual equilibrium in pure-current flows over a range of Shields parameters characteristic of both clear-water and live-bed regimes. This validation complements previously demonstrated accuracy for the same model in simulating pipeline scour processes in pure-wave environments. The model was subsequently utilized to simulate combined wave-plus-current scour over a wide range of combined Keulegan--Carpenter numbers and relative current strengths. The resulting equilibrium scour depths and trends were shown to be in accordance with existing experimentally based expressions from the literature. The variety of scour profile types emerging under various flow conditions is detailed and reconciled with experimental observations. The resulting matrix of scour depth time series was systematically analyzed, resulting in a new generalized expression for the scour time scale in combined waveplus-current flow environments. This expression is fully consistent with existing experimentally based relations at both pure-current and purewave limits and is appropriate for engineering use. [ABSTRACT FROM AUTHOR]