No abstract

Initial ship design necessitates the evaluation of main ship parameters in order to obtain a feasible design solution satisfying the design objectives. Traditionally, relationships between the main dimensions and design parameters of proven designs provided the basis of a successful and safe solution. This approach restrains the designer from improving the design with respect to possible conflicting design criteria. Pareto frontier technique has widely been utilized in the design of ships, mainly at the advanced design stages for multi-objective optimization problems. As the principal dimensions of a ship, are vital on the performance of a vessel, major improvements in performance may be achieved by selecting “better” principal dimensions. This paper proposes to integrate in the Pareto  technique studied earlier by the authors, the EEDI perspective at an early stage in the  a decision-making process for the selection of better  main dimensions with respect to multiple conflicting criteria. The previous work on the subject showed that rather promising results could be obtained for fishing boats, naval ships and planning hulls.  In this case additional requirements are included in the selection using the expected fuel consumption into the owner requirements. The study is now limited to displacement type vessels and well known and tested resistance, seakeeping and propeller algorithms.   A Pareto Front has been observed for all cases studied and is seen as a technological barrier for the ship performance with respect to main dimensions. We believe that the procedure developed reduces future conflicts in the design along the design spiral and satisfying the EEDI fuel reduction requirements. The improved performance of the design with respect to the conflicting design criteria at the initial stage of design also serves as a better basis for further optimization.

RANS-CFD is a well-established tool with widespread use in maritime industry and research. Valuable information might be extracted from the results of such simulations in terms of ship resistance and flow field variables. With recent advancements in computational power, it became possible to investigate the performance of ships in self-propulsion conditions with RANS method. This paper presents the results of a study in which self-propulsion analyses of a small size product/oil tanker has been carried out at ship scale. The methodology proposed in this study makes use of open water propeller performance predictions, resistance analyses at model scale and self-propulsion computations at ship scale for a minimum of 2 different propeller loadings to obtain the self-propulsion point and respective performance parameters. In order to speed up the time-consuming self-propulsion computations, these cases have been solved with a single-phase approach. Resistance predictions have been compared with experimental findings. Uncertainty associated with prediction of resistance and thrust has been quantified. Additionally, sea trials have been conducted on the subject vessel and its two sisters and measured delivered power data have been used for evaluating the capability of the numerical method in self-propulsion predictions. Comparison of results indicate that the proposed self-propulsion computation methodology with RANS CFD at ship scale is capable of predicting delivered power with sufficient accuracy at an acceptable computational cost.