LARGE SCALE HYDRAULIC MODEL EXPERIMENT ON SCOUR PREVENTION EFFECT AND SCALE EFFECT OF THE MODEL OFFSHORE WIND POWERFACILITIES BY FOOT PROTECTION BAG

Abstract

 Monopile offshore wind turbines require scour prevention work because the seabed around the monopile is subject to scouring by waves and currents. In this study, we conducted a large 1/9-scale hydraulic model experiment to investigate the scour-preventing effect of foot protection bag, the necessity of a filter layer, and the scour scaling effect of the hydraulic experiment. As a result, the scour depth was greatly reduced to 1/3~1/4 by the installation of the foot protection bag. The best scour prevention effect was achieved when the bags were laid in a circular arrangement overlapping each other. The installation of a filter layer under the bag material greatly improved the scour prevention effect. Under conditions without bag material, scour is reproduced even on a small scale of 1/60 according to the settling velocity parameter. However, in the case of the bag material, the velocity at the bottom of the bag tended to be smaller, resulting in a smaller scour depth.