Modelling the roughness effects of marine coatings and biofouling on ship frictional resistance

Student thesis: Doctoral Thesis

Abstract

The answers to the question, “How might the roughness of coatings and biofouling be related to full-scale ship resistance and powering?” were sought in this research, and novel contributions were made to the state-of-the-art knowledge.The current techniques used for predicting the roughness effects of marine coatings and biofouling on the resistance of full-scale ships rely on assumptions from similarity law scaling and boundary layer theory. Although this is a reasonable method, it may be difficult for less experienced users to carry out such an analysis since similarity law scaling includes several numerical procedures which may cause numerical errors and requires deep knowledge of the subject. It would also be beneficial to propose alternative methods with which to accurately predict these effects using fully-nonlinear Computational Fluid Dynamics (CFD) models, since current technological advances offer computational power which can be utilised to perform simulations based on Reynolds-Averaged Navier-Stokes (RANS) approaches.This work mainly aims to model the roughness effects of marine coatings and biofouling on ship resistance and powering, and to develop and propose alternative models for this purpose.Firstly, drag characterisation of several marine coatings, including the novel paints developed within the EU FP7 FOUL-X-SPEL Project, as well as control surfaces, was made through towing tests of flat plates coated with such coatings. An in-house code based on the similarity law scaling was then developed. This was used to assess the roughness effects of different marine coatings, including FOUL-X-SPEL Paints, and different fouling conditions on the frictional resistances of flat plates of ship lengths. Added resistance diagrams were generated using these predictions.Following this, two separate CFD models were developed and proposed for the prediction of the roughness effects of marine coatings and biofouling using flat plates of both model-scale and full-scale. These models were validated against an experiment and compared with the similarity law scaling, respectively.Afterwards, unsteady RANS CFD simulations of the roughness effects of marine coatings and biofouling on the full-scale KCS hull appended with a rudder were performed, using the roughness models proposed earlier, in order to arrive at a final conclusion.Finally, some discussions and conclusions on the outcomes of the work performed within this thesis are presented.This author believes that this study has shown the applicability of the CFD-based method to investigate the roughness effects of marine coatings and biofouling on ship frictional resistance. The CFD methods and added resistance diagrams proposed in this thesis stand as practical prediction methods for both academia and industry.
Date of Award1 Jan 2015
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorAtilla Incecik (Supervisor) & Osman Turan (Supervisor)

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