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HYDRA: Multipurpose ship designs in engineering and education
Published in Pentti Kujala, Liangliang Lu, Marine Design XIII, 2018
R.J. Pawling, R. Bilde, J. Hunt
Hullform type and material were selected using a Strengths-Weaknesses-Opportunities-Threats (SWOT) and Weight-Score Method (WSM). Four hullform types were considered: Catamaran (SWATH); Trimaran; conventional catamaran; and conventional monohull. Table 3 gives an example analysis for the catamaran-SWATH option and Table 4 summarises the WSM analysis for hullform type, with the monohull option being preferred. The WSM analysis for structural material compared steel, aluminum and carbon fibre composite, with steel being selected.
Prediction of maneuvering coefficients of Delft catamaran 372 hull form
Published in Petar Georgiev, C. Guedes Soares, Sustainable Development and Innovations in Marine Technologies, 2019
Researches related to this topic are relatively new. Javanmardi (2008) developed a CFD code that is capable of simulating hydrodynamics of rigid bodies under 3-D, time-dependent, multi-phase and viscous conditions. The resistance and maneuvering performance of a trimaran hull constructed by Wigley hull form which can be represented mathematically, under 6-DoF were investigated by this in-house code. Larger steady turning diameters were reported for side-hulls located close to the fore part of the vessel. It was concluded that side-hull placement has great effects on resistance and maneuvering performance. Van’t Veer (1998) performed an experimental study to assess the resistance and seakeeping characteristics of the Delft372 catamaran (DC372) which was designed at Delft University. Castiglione et al. (2011) studied the seakeeping characteristics of DC372 in high sea states with URANS. Their results indicated that the CFD based on URANS is a valid tool in the solution of seakeeping problems. Milanov et al. (2012) presented a study on system-based maneuvering simulation of DC372. Fast-time maneuvering simulations (FTMS) were achieved by using the maneuvering coefficients obtained from PMM tests. Then, free running model experiments were conducted for a set of water depth ratios and Froude number values to compare the simulation results. The maneuverability and directional stability of the vessel were estimated. Manivannan et al. (2013) presented a system-based simulation application for water-jet equipped DC372. A decrease of 11% in required power for propulsion were saved by using high fidelity method. Dogan (2013) studied the vorticial structures, turbulent structures and instabilities of the DC372 by DES solver CFDShip-Iowa V4.5 in collaboration with NATO AVT 183. A series of static drift simulations with URANS and DES were performed and the numerical results were compared with the experimental ones that measured at different facilities. Good agreement between EFD and CFD for the forces was reported while larger errors were observed for the moment and motions. Broglia et al. (2014) conducted an experimental study on the wave interference phenomena between demi-hulls. DC372 hull form was chosen for the model tests that were carried out at a range of 0.1–0.8 Froude number. The demi-hull clearance was changed parametrically and tests were repeated for all advance speeds. As it was observed, total resistance increased in catamaran case in the most testing conditions. Maximum increase in total resistance was detected at the smallest demi-hull clearance case which was about 30%. It was emphasized that the inner and outer fields should be analyzed with caution to be able to understand the wave interference phenomena. Falchi et al. (2014) presented a work on the measurement of velocity field around a catamaran in oblique towing condition with Stereo-PIV. The static drift tests were carried out at 0.4 and 0.5 Froude numbers and drift angles were 6 and 9 degrees. The model was fixed at dynamical values of sinkage and trim in all the tests. Characteristics of the keel vortices were documented and a valuable experimental dataset for CFD benchmarking were provided.
A simplified methodology for dynamic responses of cross-decks of trimarans under slamming loads
Published in Ships and Offshore Structures, 2023
Zhanyang Chen, Weidong Zhao, Xiyu Liao, Mengchao Du
Compared with traditional types of ships, trimarans have significant advantages, such as smaller wave resistance, better lateral stability and seakeeping performance. Ships with complex structures and high speed are subjected to the slamming phenomenon frequently in the serious sea states (Xia et al. 2011; Lavroff et al. 2013; Lind et al. 2015). In the slamming process, the temporal and spatial distribution characteristics of slamming pressure on hull structure are related to many factors, i.e. water entry velocity, structural geometric surface, etc. Therefore, it is not easy to describe with mathematical models. In particular, the high-speed trimarans have side hulls and cross-decks, making the slamming response analysis of local structures more complex.
Effects of nearshore wave reflections on the behaviour of an axe bow trimaran hull
Published in Ship Technology Research, 2021
Christopher Lewis McGibbon, Md Jahir Rizvi
A trimaran vessel constructed with a central and two outer hulls generally provides static and dynamic stabilities that are exemplary due to its unique features such as very wide beam, low draught and slender hulls. In addition, a trimaran hull offers excellent seakeeping performances in wavy seas, reduced wave making resistance and increased fuel efficiency at high speeds; provides large deck areas and allows access to the areas that are inaccessible for its mono-hull counterparts (Fang and Chen 2008; Hafez and El-Kot 2012; Luhulima et al. 2014). The righting arm or the GZ value is an important parameter of a hull to identify its stability characteristics. It is well established that the higher the GZ values, the better the statical and the dynamical stabilities. The maximum GZ value occurs for a trimaran hull at a very low angle of heel compared to that of any monohull and/or even catamaran vessels. This means a trimaran hull requires high energy input in order to heel to a small angle. Due to these advantages, trimaran hull was able to attract the attentions of naval architects and had been proved to be second to none as high-speed commercial and naval vessels (Fang and Chen 2008). However, the sizes of the outer hulls and the transverse distances of those outer hulls from the central hull directly affect the flow behaviours and these, in turn, affect the hydrodynamic performances of a trimaran vessel. A number of researchers (Fang and Chen 2008; Yu et al. 2015) suggested that the sizes of the outer hulls and its distances from the central hull should be optimized for all headings to maximize the hydrodynamic behaviours of a trimaran vessel. In addition, shifting the longitudinal positions of the two outer hulls towards forward (i.e. putting at a position further away from the stern) may reduce wave loads (Fang and Chen 2008). Tang et al (2016) investigated the motion behaviour and the vibration responses of a trimaran hull subjected to oblique waves. They found that both heave and roll motions are sensitive to beam seas, whereas pitch motion is severe in following seas. Furthermore, slamming and whipping loads for trimaran vessels are severe in heavy seas. Katayama et al. (2009) identified that high-speed trimaran hull experiences parametric rolling in head seas. This type of rolling can cause severe passenger and crew discomforts, extreme pressures on the hulls, non-linear propeller torque and reduced stability. Thus, trimaran hull should be designed carefully to avoid such rolling motions.