The correlation of added drag with surface roughness parameters

Abstract

Drag reduction in the marine environment means inhibiting fouling and reducing paint surface roughness. The conventional method of measuring ship hull surface roughness is discussed followed by an account of the available experimental evidence where the roughness functions and corresponding painted surface roughness characteristics have been measured in the laboratory. Twenty eight such surfaces are identified. The correlation of the roughness functions with surface geometry is then discussed and the most recent results described. Possible future developments are outlined to eliminate fouling, reduce roughness to the ‘hydraulically smooth’ datum and then to further reduce drag noting that most fish do not foul and there is some evidence of drag reducing mechanisms.