Thesis
Investigation of trim influence on resistance, seakeeping and propulsive performance
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2023
- Thesis identifier
- T16523
- Person Identifier (Local)
- 201580581
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- There has been a lot of interest in recent years in trim and ballast optimisation in which the ballast of a vessel is varied to reduce fuel consumption and greenhouse gas emissions. Trim optimisation is one of the easiest and cheapest methods among many fuel-saving measures recommended by IMO as it does not require any hull shape modification or engine upgrade. Many existing ships are designed for a single operational condition with the aim of producing low resistance at their design speed and draft with an even keel. Given that a ship will often sail outside this condition over its operational life, the effect of trim on ships resistance and powering will be significant. However, limited research has been performed to investigate trim influence on ship performance. In many cases, the work has concentrated on minimisation of resistance; often focussing on calm-water resistance in model scale. The impact of trim on added resistance and propulsive performance of ships is less well understood. In this context, the main aim of this PhD study is to gain an improved understanding of the impact of trim on the resistance, seakeeping and propulsive performance of vessels by using Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD) methods. This study covers model tests in towing tank, model scale and full scale CFD analyses for various operating points in calm water and waves. This study consists of three main parts. In the first part, trim influence on the calm water resistance of the KRISO Container Ship (KCS) was investigated. A series of resistance tests for various trim angles and speeds were conducted at 1:75 scale at design draft. CFD computations were carried out for the same conditions and also for ballast draft with the hull both fixed and free to sink and trim. Trim influence on individual resistance components was discussed. Full-scale numerical simulations are also carried out and differences between model scale and full-scale findings are discussed to investigate scale effects on optimum trim. In the second part of this study, the effects of trim angles on added resistance and motion responses of KCS were evaluated experimentally and numerically in six different trim angles. Effects of trim angles on added resistance were analysed and results concerning the performance of the vessel at different trim angles were plotted. Experimental and numerical results for the heave and pitch motions and the added resistance were compared. Furthermore, the range of trim and wave conditions were identified for the application of the rapid linear potential flow method. The study is then extended to include a model of the propeller to investigate the trim influence on the propulsive performance of the KCS. Self-propulsion simulations were performed using two different methods, namely, sliding mesh with 3-D propeller geometry and body force method based actuator disk approach. Effects of trim angles on propulsive characteristics were analysed and results concerning the performance of the vessel at different trim angles were plotted. The differences in optimum trim based on pure resistance simulations and self-propulsion simulations were investigated. As trim optimisation studies require the analysis of large number of different operating conditions, the applicability and accuracy of a quicker simplified actuator disk approach was tested. This author believes that methods and findings presented in this study contribute towards better understanding of the trim influence on resistance and powering performance of ships. Additionally, these findings may be used to further develop accurate and efficient trim optimisation tools for minimizing fuel consumption and emissions accordingly.
- Advisor / supervisor
- Khorasanchi, Mahdi
- Turan, Osman
- Day, Sandy
- Resource Type
- DOI
- Date Created
- 2021
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