A passive suspension system for a hydrofoil supported catamaran
Date
2008-03
Authors
Kopke, Markus
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
This study investigates practical passive methods to improve the seakeeping of a
Hydrofoil Supported Catamaran (Hysucat). The Hysucat is a hybrid vessel combining
hydrofoil efficiency with the stability of catamarans.
The seakeeping of the Hysucat was initially investigated experimentally to determine
what seakeeping improvements are inherent to the Hysucat design. The results
showed that the seakeeping is improved by 5-30%.
A passive suspension system for the main hydrofoil of the Hysucat was designed and
tested. A concept development strategy was followed for the design of the suspension
system as such a system had never been investigated previously. Detailed
specifications for the design were developed and concepts that could satisfy the
customer and engineering requirements were generated.
Numerical simulation models for the Hysucat and the final concepts were derived
assuming a simplified 2nd order system to describe the seakeeping dynamics of the
demi-hulls. Unknown parameters were determined using parameter estimation
techniques. Representative parameter values were calculated from multiple towing
tank experiments. Theory describing the motion of a hydrofoil in an orbital velocity
wave field was combined with the hull model to simulate the Hysucat as well as the
suspension system concepts.
The models indicated that the concept where the main hydrofoil was attached to a
spring loaded arm, that was free to pivot in response to orbital waves, was the most
feasible in damping out vertical transmitted accelerations. Experimental tests indicated
that little improvement was achieved with the suspension system at low frequencies. At
resonance the suspension system was effective in decreasing the heave of the vessel
by up to 27%. The pitch and acceleration response results showed improvements at
the higher encounter frequencies of up to 50%. The calm water resistance of the vessel
increased by 10% over the Hysucat with rigidly attached hydrofoils; however was still
24% less than the hull without foils.
Description
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008.
Keywords
Hysucat, Seakeeping, Dissertations -- Mechanical engineering, Theses -- Mechanical engineering, Hydrofoil boats -- Design and construction, Catamarans -- Design and construction, Ships -- Hydrodynamics