Impacts of different characteristics of marine biofouling on ship resistance

Abstract

Ship resistance research on marine biofouling is an old but hot topic which invokes plenty of studies recently. Previous studies on the surface roughness of ship hulls mainly focus on the height of micro-organisms or macro-organisms adhered to ship hulls without considering other components which may indeed play an important role in generating additional resistance. Many authors attempt to use a single parameter, for example, height of the biofoulers, to describe the hull roughness. Our research indicate that any single factor affecting ship hull roughness can not completely reflect the compositions of ship resistance. Here we propose a novel numerical model which enables more precise estimates of the contribution of each single component involving in the marine biofouling.The standard k−ε model of FLUENT is modified by considering the possible rotating, jetting, surging and swirling of fluid flowing over ship hulls due to characteristics of the marine biofoulers. Simulated results using the modified model at various speeds are compared with that using the original model, and an improvement of ship resistance is evident, quantitatively consistent with measured, indicating that the modified model behaves in a reasonable manner in simulating the relationship between ship resistance and ship surface roughness.The marine biofoulers affect ship resistance primarily by increasing the tangential surface shear stresses. Simulated results demonstrate that additional resistance caused by height, shape, hardness and density of the biofoulers accounts for up to ∼80% of total resistance in the heavy fouling condition (taking vessel “YOURIXX” as an example), implying an economic demand for good hull performance.