The effect of cleaning and repainting on the ship drag penalty
I Ketut Aria Pria Utama, Bagus Nugroho, Marwan Yusuf, Fredhi Agung Prasetyo, Muhammad Luqman Hakim, I Ketut Suastika, Bharathram Ganapathisubramani, Nicholas Hutchins, Jason Monty
Abstract
Although the hull of a recently dry-docked large ship is expected to be relatively smooth, surface scanning and experimentation reveal that it can exhibit an “orange-peel” roughness pattern with an equivalent sand-grain roughness height ks = 0. 101 mm. Using the known ks value and integral boundary layer evolution, a recently cleaned and coated full-scale ship was predicted to experience a significant increase in the average coefficient of friction %ΔC¯f and total hydrodynamic resistance %ΔR¯T during operation. Here the report also discusses two recently reported empirical estimations that can estimate ks directly from measured surface topographical parameters, by-passing the need for experiments on replicated surfaces. The empirical estimations are found to have an accuracy of 4.5 − 5 percentage points in %ΔC¯f.