Townsin's formula vs CFD: Evaluating hull roughness effect in ship resistance

초록

This study aims to cross-validate two methods for predicting effects of hull roughness: Computational Fluid Dynamics (CFD) simulations and Townsin's formula. Since its establishment in 1990, as a standard in the ITTC 1978 method, Townsin's formula has been utilised for over three decades, consistently yielding reasonable results. However, its empirical nature and omission of detailed scientific flow characteristics have been points of contention among some experts. In this study, this formula is compared with the contemporary CFD approach using modified wall functions. Full-scale CFD simulations were conducted on benchmark hull forms KCS and KVLCC2, incorporating the roughness effects of typical antifouling coatings. The results predicted by Townsin's method and CFD simulations were compared through two separate analytical approaches. It was observed that the level of concordance between these methods varied based on the analytical approach taken. This analysis revealed that Townsin's formula accounts for not only the roughness but also form effect in frictional resistance, resulting in good agreement with the CFD simulations.

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