Time-dependent biofouling growth model for predicting the effects of biofouling on ship resistance and powering

Abstract

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 3-years 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.