Resistance Prediction, Hull Optimization And Series Model Tests Of Trimarans

From the day ship appeared, speed increasing is always one of the important attempts. The 21th century is the century of the ocean, enhancing the ability of controlling the sea and making use of the ocean resourses become a strategical aim. Exploitation and transportation have a great relationship with the ship performance, various countries recognize that high speed is an emphasis of ships in this century. Comparing with mono-hull ship and other vessels, trimaran has a lot of advantages, and gets attention in the recent years.The developments of both military and commercial ships have become a heated point, there are already several trimarans been built and put into uses. And, the development of trimaran is also a need for the recently highly concerned issues of energy saving and emission reduction in sea transportation.Trimaran has many advantages in hydrodynamic properties, but the existence of the two outriggers makes the flow field around it complex, and causes the interference among the hulls. There are many factors effecting the characteristics, such as the positioning of the outriggers and the shape of the hulls, when considering the configuration of the trimaran, one must take the friction resistance, wave making resistance and other factors into account. In this paper, the author investigates mainly the resistance performance, relationship among configuration, main particulars and other factors of trimaran.Firstly, three trimarans with nine different configuration of the trimaran are investigated with a modified New Slender Ship Theory method, the resistance is predicted, and the comparisons of the results with the experimental data show good agreement, indicating that the method is effective in calculation of resistance of the trimaran.Then an optimizaton is made by use of a technique of constrained hull optimization method with the combination of nonlinear programming and wave making resistance calculation of trimaran, and test models are made for the parent and optimized trimarans, and tested in towing tank. The comparisons show that apparent improvement has obtained in higher speed range as predicted, showing the effectively of the optimization method.After these, on the basis of the optimized trimaran, a series model tests are conducted for resistance, with the variations of some hull parameters such as configuration, length to beam ratio of the center hull, displacement ratioes of triggers with the center hull. Based on the results, detailed analyses are made for the components, characteristics of residuary resistance, and the relationship among configuration, main particulars and interference of waves caused by the three bodies of trimaran separating the trimaran into centerhull model and the catamaran consisted of its triggers, conducting resistance tests separately, adding the drags of these two models to get the"non-interference resistance"as correspondance of the resistance of the trimaran, investigation is made for the relation of above"non-interference"and"interference"drags, as well as the influence of configuration, displacement ratio etc. on the drag, and discuse the"favorable"and"infavorable"interference of wave making resistances, the corresponding configuration. And, scaling the trimaran, a well-performance round bilged and a deep V monohull to the same displacement, compare their resistance performance, analyse their suitable speed ranges.Finaly, integrating the above mentioned series tests and analysing their results, a trimaran resistance chart is formed, which can be used as reference in the preliminary design and the analysis of resistance performance of trimarans.