Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2005. / This work is concerned with the design and hydrodynamic aspects of a hydrofoil-assisted
trimaran. A design and configuration of a trimaran is evaluated and the performance of a
hydrofoil-assisted trimaran is effectively compared to the performance of a hydrofoil-assisted
catamaran with similar overall displacement and same speed. The performance of the trimaran
with different outrigger clearances are also evaluated and compared. The hydrodynamic aspects
focuses mainly on the performance and to a lesser extend on the sea-keeping and stability of a
hydrofoil-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 of
the hydrofoil-assisted catamarans and due to the fact that there does not exist a hydrofoil-assisted
trimaran (to the author’s knowledge) where the main focus of the foils is to significantly reduce
the resistance.
A brief history, recent developments and associated advantages regarding trimarans are
discussed. A complete theoretical model is presented to evaluate the lift and drag of the
hydrofoils, as well as, the resistance of the trimaran. The data so obtained is then used to compare
the reliability and feasibility of the numerical and experimental predicted values.
The design of the trimaran and hydrofoil system is explained, together with the problems
associated with the final design of the trimaran. The design of a trimaran is much more
complicated than a catamaran due to more design variables being associated with trimarans. The
selection of the trimaran configuration is done in a logical manner considering stability and
hydrodynamics. However, the hydrofoil-assisted trimaran is closely adapted to the main
dimensions of the comparable hydrofoil-assisted catamaran.
An in-depth discussion of the testing technique used and the problems that are associated with
towing tank testing will facilitate similar tests in the future. The scaling method of Froude was
modified to account for the different sized hulls. The numerical methods are explained, with
emphasis 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 carried
out. The resistance, trim and rise/sinkage results are presented with speed for both the trimaran
and catamaran with and without the addition of foils. The addition of the foils supplies results
based on the amount of lift the foils carry and therefore can easily clarify the significant
resistance 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 the
catamaran with similar displacement and speed is still superior to the trimaran, with and without
foils 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 future
work.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2005 |
| Date | 12 1900 |
| Creators | Moolman, Ryno |
| Contributors | Migeotte, G., Harms, T. M., University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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