12 - Hull roughness and ship resistance

Abstract

This chapter assesses the hull roughness and ship resistance taking into account the spectral bandwidth and the moments of the spectrum that are essential concepts in the associated theory of surface metrology. The chapter also explains about how the ideas of spectral analysis have been transferred in recent years to a discipline which traditionally did not view its data as random. In linking surface metrology and ship resistance, there is a need to divide ship hull geometric irregularities into at least two categories. Spectral analysis has also been used to assess the appropriateness of differing filtering techniques. The state of the art in terms of internationally accepted ideas can be determined by reading the proceedings of the International Towing Tank Conference held in Madrid in September 1990. Spectral analysis related software is now available as a standard option on some of the better laboratory bench stylus surface profilometers. It is now accepted that a correlation between added drag and ship hull surface statistics does exist and it is important to understand this if ships are to be operated economically.