Scale Effects in Heave Plates: PIV Investigation

Abstract

Bezunartea et al. Scale Effects on Heave Plates for Semi-Submersible Floating Offshore Wind Turbines: Case Study With a Solid Plain Plate (Journal of Offshore Mechanics and Arctic Engineering, Vol. 11, pp 1–14, 2019) studied scale effects on the hydrodynamics of heave plates by conducting model scale experimental tests. Three models with different scales of one leg of the HiPRWind platform, equipped with a plain heave plate, were built and tested with forced harmonic heave motions. They showed that the influence of the model scale on the coefficients is clearly weaker than that of the heave motion amplitude. Among the pending tasks in that work was to conduct velocity field measurements of the flow with Particle Image Velocimetry techniques (PIV). This paper discusses some of the results of such measurements, carried out forcing vertical harmonic motions. In these measurements, it is assessed how significant scale effects are also in the local kinematics of the flow, thus complementing the global ones carried out in the referred work. From velocity and vorticity graphs, the flows show great similarities across the three scales, consistent with the ones found in the prequel paper. A metric has been developed whose outcomes are aligned with these results but further work is necessary to develop key indicators to compare flow fields from PIV across different scales.