Hull and propeller roughness can be caused by various factors such as mechanical causes, chemical and electrochemical processes (e.g. corrosion), and finally the colonisation of biofouling, which is often the most critical. The associated economic and environmental problems include increases in ship resistance, fuel consumption, and greenhouse gas emissions. The mitigation measures are also associated with costly antifouling coatings and dry docking. Therefore, accurate predictions of the roughness effect on ship performance are of great importance in the economic and environmental perspectives. Although many studies have been carried out to investigate the roughness effect since the age of William Froude, our understanding in this field is still limited. More specifically, the validations of the two most prevalent prediction methods are not complete. Also, the conventional studies have mainly focussed on the roughness effect on ship resistance, whereas the impact on propulsion performance has been less highlighted.Furthermore, the hull surfaces have been treated as uniformly rough in the conventional studies, while real ships’ surfaces are not uniform as they are exposed to heterogeneous fouling accumulation. Based on the above background, this PhD study aims to develop computational and experimental techniques to investigate the effect of biofouling on ship hydrodynamic performance. This aim has been realised by achieving several milestones using Computational Fluid Dynamics (CFD) and Experimental Fluid Dynamics (EFD).This PhD thesis consists of three distinct parts. Part I includes experimental validations by means of tank testing to demonstrate the suitability of the methods for the added resistance prediction due to hull roughness: Granville’s similarity law scaling method and the CFD method involving modified wall-functions. Part II presents the full-scale applications of the CFD approach to predict the effect of biofouling on the full-scale ship hydrodynamic problems, including ship resistance, propeller performance and ship self-propulsion performance. Finally, extended investigations are presented in Part III, including the investigations into the effect of heterogeneous distributions of hull roughness on ship resistance as well as the roughness effect with the variations of hull forms, ship lengths and speeds.
|Date of Award||28 Jul 2020|
- University Of Strathclyde
|Sponsors||University of Strathclyde|
|Supervisor||Yigit Kemal Demirel (Supervisor) & Mehmet Atlar (Supervisor)|