Scale Effects on Heave Plates for Semi-Submersible Floating Offshore Wind Turbines: Case Study With a Solid Plain Plate

Abstract

In the case of SPAR or semi-submersible platforms for floating wind turbines, it is beneficial in some cases to use heave plates that reduce their heave motion amplitude and/or tune their heave natural period. As part of the Hiprwind project, it was decided to study scale effects on the hydrodynamics of this element. To this aim, models of one leg of the platform, equipped with a heave plate without any reinforcements, were built. This model is a simplified representation of the actual one, which incorporates a vertical flap on the heave plate edge. The scales were 1:20, 1:27.6, and 1:45.45, with the former leading to added mass values of the order of 300 kg, becoming one of the largest models for which experiments with heave oscillations have been carried out. Decay tests starting from various amplitudes and forced oscillations tests for a range of frequencies and amplitudes were performed. It is shown in the paper that the influence of the scale factor on the hydrodynamic coefficients is weaker than the effect that the motion amplitude (characterized with the Keulegan–Carpenter (KC) number produces in them. This result is relevant because the selection of a representative KC is an important and somewhat arbitrary aspect to be set in the linear potential simulation codes in order to add viscous damping. What has been shown herein is that a right selection of KC has a larger impact on the models than the uncertainties due to eventual scale effects in the heave-plates dynamics.

A Review of Research Status and Scientific Problems of Floating Offshore Wind Turbines

“…The most ideal state of the model test is that it meets the mechanical similarity and thermal similarity with the prototype. For blades of the wind turbine, the heat transfer is generally ignored, that is to say, they need to meet a mechanical similarity: geometric similarity, kinematic similarity and dynamic similarity [22].…”

Validation Study of a CFD Numerical Solver for the Oscillatory Flow Features Around Heave Plates

“…Model tests were done with and without reinforcement on the heave plate [7]. Scale effects on the forces and flow fields were presented in [17].…”

“…The vorticity fields in the fluid domain are compared to the experimental results obtained by Particle Image Velocimetry (PIV) methods presented by Anglada et al (2020). We calculate the hydrodynamic loads on the cylinder with the heave plate and compare them with the experimental results previously published by Bezunartea et al (2020).…”

Study on the Influence of Chamfer Perforation on Heave and Pitch of a Single Floating Platform

“…Gu et al [8] simulated the forced heave and surge motion of axisymmetric vertical cylindrical bodies with flat and rounded bases and determined the viscous effects generating drag, as well as influencing added mass and radiation damping. Bezunartea et al [9] built models of one leg of a platform that was equipped with a heave plate without any reinforcements, to study scale effects on the hydrodynamics of this element. Alexander et al [10] developed an open-source CFD/6-DOF solver by using OpenFOAM for the high-fidelity simulation of offshore floating wind turbine platforms.…”