An investigation into the effects of marine biofilm on the roughness and drag characteristics of surfaces coated with different sized cuprous oxide (Cu2O) particles

Abstract

Biofilms typically increase surface roughness and consequently the drag penalties on marine vessels. However, there is a lack of data regarding the time-dependent influence of biofilms on antifouling surface characteristics and frictional drag, especially for surface coatings with different sizes of cuprous oxide (${\text{Cu}}_2\mathrm{O}$). In this study, a series of pressure drop measurements was carried out using flat plates coated with different sizes of ${\text{Cu}}_2\mathrm{O}$. The cuprous oxide-containing surfaces were deployed at sea for a period of six months to allow biofilm to develop. Surface microstructure and roughness analyses were carried out every six weeks using scanning electron microscopy and laser roughness surface profilometry. From the data, the added frictional drag caused by biofilm on ships was predicted, based on roughness function using Granville extrapolations. The analyses indicated that biofilms had significant impacts by altering the surface microstructure, resulting in higher frictional drag. However, due to the interaction between the biofilm and the physico-chemical properties of the substratum for panels coated with larger ${\text{Cu}}_2\mathrm{O}$, the roughness and drag measurement results were both found to have fluctuating increments.

Keywords: added resistance; antifouling; biofilm; frictional drag; particle size; pressure drop measurement; roughness characteristic; roughness function; Cuprous oxide (${\text{Cu}}_2\mathrm{O}$).