Predictions of added resistance and the effective power of ships were made for varying barnacle fouling conditions. A series of towing tests was carried out using flat plates covered with artificial barnacles. The tests were designed to allow the examination of the effects of barnacle height and percentage coverage on the resistance and effective power of ships. The drag coefficients and roughness function values were evaluated for the flat plates. The roughness effects of the fouling conditions on the ships' frictional resistances were predicted. Added resistance diagrams were then plotted using these predictions, and powering penalties for these ships were calculated using the diagrams generated. The results indicate that the effect of barnacle size is significant, since a 10% coverage of barnacles each 5 mm in height caused a similar level of added power requirements to a 50% coverage of barnacles each 1.25 mm in height.

Predictions of increases in ship frictional resistance and powering were made for a range of barnacle fouling conditions. A series of towing tests were conducted using flat plates systematically covered with 3D printed barnacle tiles. The tests were set up to investigate the effect of barnacle settlement on the resistance and effective power of the ship. Therefore, a chaotic settlement which is called natural settlement, was designed to represent real barnacle settlement in nature. An extensive comparison was made between this natural settlement and the settlement that was designed in accordance with the standards. The drag coefficients and roughness functions values were determined and full-scale ship resistance and powering were estimated for six different ships at their cruise speed by using boundary layer similarity law. In addition, decreases in cruising speed due to barnacle fouling at fixed effective power were estimated as part of the case studies. The results indicate that settlement pattern caused up to ~10.5% difference in frictional resistance and ~6.7% difference in powering at cruise speeds whereas this settlement pattern caused up to ~20.5% speed reduction at fixed effective power.

This paper presents a time-dependent biofouling growth model which enables prediction of the effect of biofouling on ship resistance and powering for day-to-day evaluation. Initially, antifouling coating tests data were employed in the model to predict coating performance over time by considering the ship operating profile and shipping route. Based on the equivalent sand roughness heights found in literature, time-dependent biofouling growth predictions were turned into equivalent sand roughness heights. Then, the provided roughness functions for different surface conditions as well as the predicted equivalent sand roughness heights were employed in Granville's similarity law scaling to investigate the effect of roughness on full-scale ship resistance.Then, the model was tested through one-year long operation data of a 176 m long tanker measured by on-board systems to validate the model. Percentage increase in frictional resistance of the 176 m long tanker was predicted to be ~32%. Results were compared and validated using real data. Secondly, a case study was performed using noon-report data for 3years operation of a 258 m long crude-oil carrier. Increase in effective power of the ship was predicted to be ~25%. Finally, the predictions were compared to ship performance reports that were provided by the ship operator.

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