Catamaran In Waves Research Articles

A study on the added resistance of a catamaran advancing in waves considering variations of both operating and geometric parameters

ABSTRACT The study focuses on the analysis of the added resistance of a catamaran advancing both in regular waves and in a seaway. The numerical simulation has been carried out within the framework of potential flow theory by using a three dimensional, linear, Rankine source-based Boundary Element Method (BEM) and a Near-Field approach based on pressure integration for the first-order motions and the second-order longitudinal force prediction, respectively. A preliminary validation and verification study on both a mono-hull and a catamaran is proposed. A systematic analysis of the effect of some relevant operating and geometric parameters on the added resistance performance of a catamaran in waves is presented. Variations of the operating and geometric parameters include the advancing speed, the encounter angles from head to beam waves, the hull static trim and the demi-hulls separation. The trends of the added resistance pseudo-RAO are discussed in the light of the comparison against the reference design condition highlighting possible worse and optimal configurations.

Seakeeping performance of a rounded hull catamaran in waves using CFD approach

Seakeeping performance of a rounded hull catamaran in waves using CFD approach

Analysis of hydrodynamic characteristics for arbitrary multihull ships advancing in waves

Multihull vessels have emerged as popular alternatives to conventional monohull ships for high-speed crafts. However, the bridging structures connecting the hulls are vulnerable to various wave actions and the wave impact on the bottom of them is the most serious problems associated with multihulled vessels. In this study, prediction of relative wave elevations under the bridging structures is investigated for multihull ships traveling with forward speed in waves. A computer code YNU-SEA using the three-dimensional (3D) Green function method with forward speed has been developed and used to analyze the hydrodynamic radiation and diffraction forces and motion responses for high-speed catamarans in waves. The results of the present calculations are compared with those of previous calculations as well as with experimental results. The numerical results reveal that the present computer code can be used as a powerful tool for the accurate numerical computation of seakeeping problems for multihull ships advancing in waves. Numerical calculations of wave pattern are also carried out including wave interactions between the hulls to analyze the effects of hull form on the free surface flow around catamarans advancing in waves. The analysis of the wave pattern allows the determination of relative wave height including radiation and diffraction waves. Finally, some discussions are included based on these numerical results which may be helpful for the accurate prediction of relative wave height and wave breaking load on the deck associated with multihull ships.

Investigation of Seakeeping Characteristics of High-Speed Catamarans in Waves

This paper presents the motion characteristics for high-speed catamarans travelling in waves. Two mathematical models, threedimensional translating-pulsating source distribution technique and three-dimensional pulsating source distribution technique, are used for predicting the motions of the wave-piercing catamaran in oblique waves. The comparison between numerical predictions and experimental data carried out in SSPA shows a good agreement except the one around the resonance regions of pitch motion. It may be due to the nonlinear effects of centre bow with large pitch motions in waves. The phase angles show some scatters in the high frequencies region at stern waves. The dynamic motions of the wave-piercing catamaran have been investigated by means of short-term statistical analysis with three-dimensional pulsating source distribution technique. The comparison of seakeeping performance between the conventional catamaran and the wave-piercing catamaran has been discussed.

Investigation of motions of catamarans in regular waves—I

In this paper an analytical technique based on the two-dimensional Green function method associated with a cross-flow approach for taking viscous effects into account to estimate the motion response of catamarans in the frequency domain is presented. In order to validate this method, the numerical results are compared with experimental values obtained for two different catamarans (ASR5061 [Wahab, R., Pritchett, C. and Ruth, L.C. 1971. On the behaviour of the ASR catamaran in waves. Marine Technology, 8, 334–360] and Marintek [Faltinsen, O., Hoff, J.R., Kvalsvold, J. and Zhao, R. 1992. Global loads on high speed catamarans. 5th Int. Symp. on Practical Design of Ships and Mobile Units, University of Newcastle-upon-Tyne, 1.360–1.373]). In the second part of the paper the tests carried out with a third catamaran configuration at the Hydrodynamics Laboratory of the University of Glasgow are presented to evaluate the non-linear effects. These test results cover different speeds and wave heights at a wide range of wave frequencies. The paper concludes that the two-dimensional method correlates very well with measurements of small amplitude motions. For large amplitude motion tests, the non-linear effects become significant when the model speed and wave amplitudes increase. The peak values of heave and pitch motions measured around the resonance frequency are smaller than those obtained from the linear theory.