Drag Penalty Causing from the Roughness of Recently Cleaned and Painted Ship Hull Using RANS CFD

Abstract

The issue of global warming makes energy savings on ships compulsory. One of the

biggest causes of energy waste is the increase in friction resistance due to the hull

roughnessthat makes not hydraulically smooth. The process of cleaning and repainting

the ship hull turned out to make a roughness that can provide a drag penalty. An

investigation using a resolved Reynolds-averaged Navier-Stokes (RANS) Computational

Fluid Dynamics (CFD) approached to assess the increase in ship resistance from a

recently cleaned and painted ship hull roughness are reported. The rough surface was

obtained through surface imprint during its annual dry-docking and digitized via a laser

scanner. A roughness geometry that was obtained from the scanning was prepared for

the CFD simulations. The results for two ships show that such surface would cause an

increase in friction resistance of the full-scale ship by 33% - 35%, which corresponds to

an increase in the ship’s total resistance by 7.5% - 28%. The type of ship that is mostly

affected by the roughness is a ship with a higher frictional resistance ratio (lower

Froude Number) compared to residual resistances, where most of them are large ships.