Towards an absolute scale for adhesion strength of ship hull microfouling

Artikel i vetenskaplig tidskrift, 2019

In-water ship hull cleaning enables significant fuel savings through removal of marine fouling from underwater surfaces. Unfortunately, cleaning may also shorten the lifetime of hull coatings, with subsequent increase in fouling growth rate. Deleterious effects of cleaning would be minimized by matching cleaning forces to the adhesion strength of early stages of fouling, or microfouling. Calibrated waterjets are routinely used for comparing different coatings in terms of adhesion strength of microfouling. However, an absolute scale is lacking for translating such results into cleaning forces, of interest for design and operation of hull cleaning devices. This paper discusses how to determine such forces, namely using Computational Fluid Dynamics. Semi-empirical formulas are derived for forces under immersed waterjets, where the normal and tangential components of wall forces are given as functions of different flow parameters. Nozzle translation speed is identified as a parameter for future research, as this may affect cleaning efficacy.