1,721,051 research outputs found
About necessary and sufficient conditions to design safe ships: the appropriate ship design process
No full textFocus of this paper is the evidence of strong interconnection between safety rules and design process especially for passenger ships. A change in the methodological approach for the safety framework might imply a strong renewal course also of the decision making process during the ship design, keeping in mind its unique peculiarities.
After a general discussion about some open issues relevant to performance-based rules implementation, some considerations are given about specific points raised by the “Safe Return to Port” capability in relation with the ship design process.
Finally, the high level of flexibility in principle guaranteed by performance-based assessment is discussed in relation with the difficulty to implement the design process as an optimization procedure, due to large amount of information involved and the
complexity of problem in terms of objective functions and constraints
The New probabilistic SOLAS: a New Era in the Design and in the Operational Life of Passenger Ships
No full textThe damage stability criteria for both passenger and cargo ships are going to change from 2009, after finalization of a long and engaging harmonization activity at IMO. Especially in the case of passenger ships. the new probabilistic methodology, significantly different from the present deterministic approach, is likely to concur at modifications of the design procedure, entailing a revision of traditional techniques toward a new perspective, able to embrace such innovative hint.
In this paper, some specific issues of the new probabilistic rules will be commented, in the opinion that such standards are an interesting but also extremely challenging resource to perform an appropriate and consistent design of future passenger ships.
The radical renewal of such standards, key reference for the ship designer, is an occasion to observe the great impact that current innovation in rule-making philosophy, and possibly in the ship design methodology, can have on the educational path that should be accordingly reviewed and worked out by academic institutions involved in this fields, in order to satisfy the requirement of an higher educational profile
Progettazione e costruzione navale: scomoda eredità o risorsa per creare futuro?
No full textCombination of design and manufacture abilities along with innovation has historically played a critical role in the shipbuilding industry. Production activities are complex and many linked industries or “cultural district” have frequently emerged in this domain. The crisis, however, is connected to overcapacity and hyper-competition, so the shipbuilding industry needs to get back to its “genetic code” of knowledge and technology intensive activities more than capital and labor intensive one.
Sommario: 1. “Indotto”, “distretti culturali” e prospettive della cantieristica navale – 2. Come sfuggire alla trappola dell’overcapacity e dell’ipercompetizione – 3.L’evoluzione e il codice genetico della cantieristica navale – 4. Un quadro di riferimento più generale – 5. Una questione di volontà e di metod
Motions and Added Resistance Calculations for Multihull Configurations
No full textIn the proposed paper, a numerical method in the frequency domain based on the Rankine source formulation, has been extended for the calculation of motions in waves of multi-hulls. Also the added resistance is evaluated by means of the direct integration of the pressure over the wetted body surface. The added resistance is therefore computed as the time averaged value of the longitudinal component of the second order force. In particular the foregoing quantities are computed for catamaran hulls at different separations..
After a brief presentation of the methodology, the vertical motions and the added resistance are computed for a combination of Froude numbers and hull separations in regular head waves. Also the single demi-hull case is considered. The catamaran investigated in this study is mainly from the NPL series for which a comprehensive set of experimental data have been published by Molland et al. [1]. The numerical analysis is also driven in the field of trimarans and the computed motions are presented for a mathematically defined hull for which experimental data are available from Colagrossi et al. [2]
The prediction of seakeeping performance and added resistance in the design of multihull vehicles
No full textThis paper is concerned about the prediction of vertical motions and added resistance in waves of catamaran
and trimaran vehicles by using a three dimensional panel method based on Rankine sources, developed at University of Genoa.
The methodology can evaluate motions in head or oblique waves provided that diffracted and radiated waves are slower
than the ship (reduced frequency > 0.25). With the purpose of validating the method and to show the possibility of its practical
use in the design of multihull marine vehicles, its application to a catamaran and to a trimaran is presented. For both these
ships experimental values are available. As a further investigation a catamaran fitted with a submerged central bulb is also
presented
Different Ballast Configurations for a 78’ Racer Cruiser Sailing Yacht: a Case Study With Particular Attention To The Stability Performance
No full textIn the field of sailing yacht design, there is a growing interest and application towards solutions for righting
moment enhancement, to be exploited when a superior capacity to counter-balance wind effect is
required.
The typical solution adopted to provide such increase in performance is the use of ballast systems, mainly
represented by the water ballast tanks or the canting keel.
In the first case the effect is obtained by transversal shift of ballast water, loaded/unloaded on board on
purpose. In the latter, the keel is able to cant for a definite angle range in order to transfer a significant
weight far from the symmetry plan.
During the design process both systems need to be attentively examined with the aim to find the best
solution in terms of interference with the yacht arrangement.
In the paper, an application study will be presented for a 78’ Racer-Cruiser sailing yacht and different
design solutions will be compared. A particular attention will be paid to the stability performance.
Furthermore, for sake of completeness, a lifting keel configuration will also be considered and commented
in terms of stability
Numerical Prediction of High Speed Catamaran Behaviour in Waves
No full textThe proposed paper examines the application of a boundary element method for seakeeping computation to catamaran hulls at different separations. After a brief presentation of the methodology, which is based on Rankine sources into the frequency domain, the vertical motions and the added resistance are computed, for a combination of Froude numbers and hull separations in regular head waves. Also the single demihull case is considered. The catamaran investigated in this study was derived from the NPL series by Insel and Molland (1992). A quite comprehensive set of experimental data for seakeeping have been further published by Molland et al. (2000).
In addition to evident validation purposes in terms of motion response amplitude operators and added resistance results, emphasis is posed in discussing the particular problem of the effects of interference caused by the reciprocal position of the demi-hulls into the various hydrodynamic problems. To this aim, comparisons at different separations of demihulls are performed for added mass, damping coefficients and exciting forces
SPH: an Experience of Application in the Naval Architecture Field
No full textThe SPH (Smoothed Particle Hydrodynamics) technique is a numerical methodology where the fluid is modelled by a number of particles which are followed during their motions from a positional and physical properties point of view. The technique was developed by Gingold and Monaghan (1977) and ndependently by Lucy (1977), initially with applications in
the astrophysics field, to simulate stellar collision, planet formation and modelling accretion disks. The significant advantage of particle methods is the possibility to study the flow, and in particular a free surface, without the necessity of mesh definition. The interest raised in ship hydrodynamics
is due both to the possibility, in principle, to correctly take care of strong unsteady non-linearities of the free surface flow and both to easily create complex geometry. In this paper, after a brief description of the methodology and following the experience derived from selected benchmark cases, a further application will be presented as a step forward to assess the
possibility of applying the methodology in the investigation of the damaged ship with water entrance.
The effects implied in the choice of some significant parameters in the procedure will be illustrated
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