Prediction of Motion and Wave Load of Mono and Twin Hull Ships in Waves

Zheng, Xing (1988) Prediction of Motion and Wave Load of Mono and Twin Hull Ships in Waves. PhD thesis, University of Glasgow.

Abstract

The main aim of this thesis is to improve the computational efficiency of three dimensional method and to investigate its applications to prediction of motion responses and wave loads for mono and twin hull vessels with emphasis on twin hull SWATH ships and crane vessels during heavy lifting operation. The result is to provide a more advanced tool for practical ship designers to use at the primary design stage. In order to improve the computational efficiency of the three dimensional theory, the existing three dimensional panel method is modified in two different manners, firstly by making use of the properties of Green's function and then by introducing the higher order panel methods. It has been found that the first approach is simple and can save considerable computation time, while the improvement by the second approach is not significant at present but it has potential for future developments. A mono hull Series 60 and a small waterplane area twin hull (SWATH) model are calculated by the modified three dimensional method (from the first approach). The emphasize is drawn on the SWATH model which is traditionally treated by the two dimensional strip theory. The viscous effect on the motion of SWATH is taken into account by a semi-empirical method. The comparison with two dimensional prediction and experimental results has been made. In addition, the standing wave phenomenon in the vicinity of twin hull ships and its effect on hydrodynamic coefficients and wave loads are extensively discussed. The ordinary motion equation is modified to predict the motion responses of crane vessels during heavy lifting operation. The coupling effect between the motion of the vessel and the load being lifted and the viscous effect are considered in the prediction. The results are compared with the available experiments to validate the prediction method. A general three dimensional method for predicting wave loads on cross deck structures of twin hull ships has been introduced. The predictions are fully three dimensional, so this method has ability to predict the wave loads and the wave load distributions at arbitrary wave heading. The predictions have been compared with experimental data. In order to evaluate the seakeeping quality of a ship design in certain ocean environment, a seakeeping quality evaluation method has been presented. This method is based on the irregular wave results which can be deriv ed from regular wave results and the observed ocean environmental data in certain area and season. In addition, some design criteria for SWATH ships have been discussed and an example has been given for evaluation of the seakeeping quality for a SWATH design. Finally, the overall conclusions regarding the above investigations are drawn, and some possible proposals for future development based on the present study are suggested.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Naval engineering
• Date of Award: 1988
• Depositing User: Enlighten Team
• Unique ID: glathesis:1988-77644
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jan 2020 11:53
• Last Modified: 14 Jan 2020 11:53
• URI: https://theses.gla.ac.uk/id/eprint/77644