Effects of ‘in-service’ conditions – mimicked hull roughness ranges and biofilms – on the surface and the hydrodynamic characteristics of foul-release type coatings

Abstract

To develop a better understanding of ‘in-service’ performance of modern marine coatings, this study explored the combined effects of different roughness ranges of foul-release coating (FRC) and light biofouling (slime) on the surface, boundary layer and drag characteristics under a range of ‘in-service’ conditions. Natural and laboratory biofilms were grown dynamically on FRC panels by exposing panels in facilities dedicated to realistic fouling culture. The boundary layer experiments were conducted in a circulating water tunnel. Boundary layer similarity-law scaling was used to predict the combined effects of coating roughness and biofilms on the added frictional resistance (% and added required effective power ) for a benchmark KRISO container ship (KCS) and a bulk carrier. The increase in due to the presence of biofilms on commercial FRC is estimated to be between 7% and 16% depending on the biofilm type, biofilm thickness and percentage coverage. Significant increases in effective power are estimated for non-fouling control primers with heavy fouling. Moreover, the paper suggests updated roughness allowances () for two vessel types assuming FRCs on their hulls with more representative hull roughness ranges and fluffy biofilms.