Comparative evaluation of a hydrofoil-assisted trimaran

[摘要] This work is concerned with the design and hydrodynamic aspects of a hydrofoil-assistedtrimaran. A design and configuration of a trimaran is evaluated and the performance of ahydrofoil-assisted trimaran is effectively compared to the performance of a hydrofoil-assistedcatamaran with similar overall displacement and same speed. The performance of the trimaranwith different outrigger clearances are also evaluated and compared. The hydrodynamic aspectsfocuses mainly on the performance and to a lesser extend on the sea-keeping and stability of ahydrofoil-assisted trimaran. The results were determined by means of experimental testing,theoretical analysis and numerical analysis. The project was initiated as a result of the success ofthe hydrofoil-assisted catamarans and due to the fact that there does not exist a hydrofoil-assistedtrimaran (to the author's knowledge) where the main focus of the foils is to significantly reducethe resistance.A brief history, recent developments and associated advantages regarding trimarans arediscussed. A complete theoretical model is presented to evaluate the lift and drag of thehydrofoils, as well as, the resistance of the trimaran. The data so obtained is then used to comparethe reliability and feasibility of the numerical and experimental predicted values.The design of the trimaran and hydrofoil system is explained, together with the problemsassociated with the final design of the trimaran. The design of a trimaran is much morecomplicated than a catamaran due to more design variables being associated with trimarans. Theselection of the trimaran configuration is done in a logical manner considering stability andhydrodynamics. However, the hydrofoil-assisted trimaran is closely adapted to the maindimensions of the comparable hydrofoil-assisted catamaran.An in-depth discussion of the testing technique used and the problems that are associated withtowing tank testing will facilitate similar tests in the future. The scaling method of Froude wasmodified to account for the different sized hulls. The numerical methods are explained, withemphasis on accuracy, limitations, feasibility and the time required to complete a calculation. The results are presented in an order suggested by the experimental and numerical work carriedout. The resistance, trim and rise/sinkage results are presented with speed for both the trimaranand catamaran with and without the addition of foils. The addition of the foils supplies resultsbased on the amount of lift the foils carry and therefore can easily clarify the significantresistance advantage the foils offer the trimaran and the catamaran evaluated in this project.The final design and results of the evaluated trimaran are discussed. It is concluded that thecatamaran with similar displacement and speed is still superior to the trimaran, with and withoutfoils in both cases. The addition of foils to the trimaran does decrease the resistance significantly.The conclusions regarding these results are presented, together with recommendations for futurework.

[发布机构] Stellenbosch University