The application of Froude scaling to model tests of Oscillating Wave Surge Converters

Experimental tank testing of scale models is a standard tool in marine engineering. The underlying problem is well understood and refinements to standard applications, like resistance testing of typical ship hulls, have led to widely accepted methodologies. Similarly Reynolds-averaged Navier-Stokes computational fluid dynamics solvers have been used to assess the effect of scaling from model to full scale for ships successfully. Problems still arise when new structures, with very different shapes or modes of motion, are tested. The OWSC is such a new structure, and this paper investigates whether Froude scaling is adequate to extrapolate model scale tank testing to full scale devices. Since only limited full scale data is yet available, the investigation is mainly based on numerical simulations. It is shown that for current designs Froude scaling of typical tank scales is probably appropriate. The application of Reynolds-averaged Navier-Stokes computational fluid dynamics methods to scaling issues in the wave energy industry is demonstrated and some challenges, mainly the demands of industry standard wall functions on appropriate mesh resolution highlighted. Although the observed changes in flow patterns seem reasonable and can be explained by changes in viscosity, some uncertainty remains on the influence of mesh resolution.