Beyond VoF: alternative OpenFOAM solvers for numerical wave tanks

Abstract

The vast majority of numerical wave tank applications are solved using finite volume-based, volume of fluid methods. One popular numerical modelling framework is OpenFOAM and its two phase solvers, interFoam and interIsoFoam, enabling the simulation of a broad range of marine hydrodynamic phenomena. However, in many applications, certain aspects of the entire set of possible hydrodynamic phenomena are not of interest and the reduced complexity could allow the use of simpler, more computationally efficient solvers. One barrier for the application of such alternative solvers is the lack of suitable wavemaking and absorption capabilities, which this paper aims to address. A wavemaking and absorption methodology is presented, which can be applied to different solvers using the same fundamental concept. The implementation is presented for interFoam and interIsoFoam, as well as two other solvers whose use as numerical wave tanks has not previously been reported in the literature, shallowWaterFoam and potentialFreeSurfaceFoam. Parameter studies are performed to guide the user in the use of the methods. Example applications for two industrially relevant test cases are demonstrated; a multi-frequency wave packet focused at one position over flat bottom and regular waves propagating over a submerged shoal. All solvers yielded useful results, but some complex wave transformations in the shoal case were only resolved by the VoF methods. Alternative methods beyond the already well established VoF methods seem worth considering because potential for significant reductions in computational effort exist.

A review on the modelling of wave-structure interactions based on OpenFOAM

“…Schmitt et al [22] explored the choice of solvers in OpenFOAM other than those based on the VOF method, which could be utilised to implement numerical wave tanks, namely: potentialFreeSurfaceFoam and shallowWaterFoam. While hundreds of publications have utilised the VOF method for WSI, Schmitt et al [22] found that less than a dozen have used shallowWaterFoam and only two have used potentialFreeSurfaceFoam.…”

A Review on the Modelling of Wave-Structure Interactions Based on OpenFOAM

“…The phase fraction on each cell face, i.e. the interpolated value, is then calculated [22] from the amount submerged below the surface cut. MPLIC is for handling multiple surface cuts, where a single cut in one cell is insufficient, e.g.…”

“…Alternative methods. Schmitt et al [22] explored the choice of solvers in OpenFOAM other than those based on the VOF method, which could be utilised to implement numerical wave tanks, namely: potentialFreeSurfaceFoam and shallowWaterFoam. While hundreds of publications have utilised the VOF method for WSI, Schmitt et al [22] found that less than a dozen have used shallowWaterFoam and only two have used potentialFreeSurfaceFoam.…”

“…Schmitt et al [22] explored the choice of solvers in OpenFOAM other than those based on the VOF method, which could be utilised to implement numerical wave tanks, namely: potentialFreeSurfaceFoam and shallowWaterFoam. While hundreds of publications have utilised the VOF method for WSI, Schmitt et al [22] found that less than a dozen have used shallowWaterFoam and only two have used potentialFreeSurfaceFoam. The potentialFreeSurfaceFoam solver is a single-phase solver, as depicted in Figure 3b, that calculates the free surface as a single-valued function, thus cannot simulate effects such as wave breaking.…”

“…waves bring partial water to go on top of a structure [40], because in this scenario the free surface is no longer a continuous boundary. More examples of using alternative models to VOF can be found in Schmitt et al [22].…”