407 research outputs found
Noise on board RO-Pax vessels: Measured levels on existing ships and new pre-normative requirements
No full textThe problem of noise annoyance on board ships has been addressed since a long time. The first document setting limits on onboard noise was the "Code on noise levels on board ships", issued by the International Maritime Organisation in 1981. More recently all the major Classification Societies introduced in their requirements the so called "Comfort Classes". They generally provide different ratings of the acoustic comfort of ships. The growing needs of passengers and workers for acoustical comfort on board pushed both Classification Societies and IMO to consider an update of limits and criteria for noise annoyance assessment. The normative framework in the field is therefore presently in an evolution phase. In the present work, a series of existing measurements of noise carried out on a set of Ro-Pax vessels is analysed and compared with the existing requirements and with the new proposals of the SILENV collaborative project (Ships oriented Innovative soLutions to rEduce Noise & Vibrations), funded within the 7th Framework Programme of the E.U. and running in the period 2009-2012. The comparison provides an indication of the possibility for shipbuilding to cope with the new requests in terms of noise performances, provided that such requests are inserted in the design process. Further efforts are needed similar to those already implemented to fulfill the present formulations of compulsory requirements and reflected in the measured values
New Requirements for Noise Radiated from Ships: Pre-normative Formulations and Background
No full textOne of the aims of the SILENV project, funded by the
E.U. within the 7FP, was the development of prenormative
requirements regarding the impact of shipradiated
noise into three different environments:
onboard the vessel and outside it, in air and in water.
The paper describes the background of the new formulations
which generally take into account the existing
requirements, the technical know-how in the field of
ship construction about the characterization of noise
source and transmission paths and the actual knowledge
of the way noise affects the various categories of receivers
involved. On these bases, objectives of the noise
control are defined in the various areas and the final
choices in terms of limits are reported, also highlighting
the motivations at the basis of the requirements. Possible
future trends in the redefinition of objectives for the
control of noise and in normative developments are also
discussed
Numerical investigation of the impact of speed reduction on propeller excitation
No full textA numerical investigation of the impact of the speed reduction achieved by pitch or propeller Revolutions Per Minute (RPM) variations on propeller performances is proposed. A test case is selected from the European Project AQUO, for which experimental data are available. Numerical self-propulsion analyses are carried out to assess the off-design propeller functioning conditions of the propeller. Results, in terms of self-propulsion points and predicted pressure pulses in the various conditions under investigation (design speed at design pitch, reduced speed at reduced pitch and at reduced RPM), are compared with the available experimental measurements. On the basis of the predicted pressure pulses and cavitation volumes, conclusions are drawn about the acoustic impact of different strategies for realizing off-design operative conditions and on the possibility of ranking them by numerical methods
L’identificazione dei personaggi nella Chronique di Ernoul e Bernard le Trésorier : strategie testuali e varianti
No full textThe Chronique that goes under the names of Ernoul and Bernard the Treasurer is a good example of the problems raised by the study of how characters are mentioned in a chronicle where, proper names refer to historical figures. The interplay between named and unnamed characters in the Chronique is not only due to the kind of historical information available to the author: it also reveals the author’s point of view on the narrative. The study of variant readings in the manuscript tradition shows how some tendencies in rewriting the text that are constant in some groups, and in some individual copies. Scribes mostly relied on the context to gather the information on the character’s names, and
sometimes on a more extensive knowledge of the text. There is only small evidence pointing to the use of external sources
Uncertainties estimates of hull girder still water loads of bulk and dry cargo ships through Monte Carlo simulations
No full text
Western Eyes on the Latin East: The Chronique d’Ernoul et de Bernard le Trésorier and Robert of Clari’s Conquête de Constantinople
No full textThe article compares the narratives on the Fourth Crusade by Robert de Clari and the Ernoul-Bernard author; their similarities may go back to the cultural milieu of Corbie abbey, that was an important centre for the production of French historiography writtent in prose at the beginning of the thirteenth century. An appendix explores the status quaestionis about Bernard the Treasurer of Corbie abbey, whose name appears in the colophon of two manuscripts of the Ernoul-Bernard Chronique
SHIP URN: UNIGE activities in the context of LIFE-PIAQUO Project
No full textIn the last years, an increasing attention has been devoted to ships Underwater Radiated Noise (URN), with the progressive introduction of Guidelines by international organizations such as IMO, Classification Societies voluntary notations, limits and incentives in specific areas. In this context, a large effort has been spent in the study of cavitating propeller noise since it represents the dominating noise source on ships. UNIGE is currently involved in the EUfunded
LIFE-PIAQUO project, in which the main activities are related to propeller design by optimization, onboard cavitation detection during operations, noise mapping. The present paper reports motivations, aims and achievements of these
activities in the first half of the project
Ship self-propulsion performance prediction by using OpenFOAM and different simplified propeller models
No full textClassic hydrodynamics-related ship design problems can nowadays be approached by CFD viscous solvers. Ship self-propulsion performance prediction represents one of the most interesting problems in this framework. The capabilities of CFD codes to resolve accurately the separate problems (open water propeller performance and hull resistance) have been demonstrated over the last decades. The complexity of the combined problem (and, in turn, the required computational time) has restricted its solution to research applications still far from everyday industrial practice. Some approaches have been developed to reduce the computational burden, based e.g. on simple actuator-disk theory or, recently, on BEM/RANS coupled solvers. In this respect, different approaches exploiting the open-source solver OpenFOAM are presented, focusing on the main self-propulsion parameters. In addition, a new numerical strategy able to provide more information compared to classical simplified approaches, is herein presented and validated against experimental measurements on the well-known Kriso Container Ship (KCS) test case
An efficient and robust approach to predict ship self-propulsion coefficients
No full textAchieving a reliable and accurate numerical prediction of the self-propulsion performance of a ship is still an open problem that poses some relevant issues. Several CFD methods, ranging from boundary element methods (BEM) to higher-fidelity viscous Reynolds averaged Navier–Stokes (RANS) based solvers, can be used to accurately analyze the separate problems, i.e. the open water propeller and the hull calm water resistance. However, when the fully-coupled self-propulsion problem is considered, i.e. the hull advancing at uniform speed propelled by its own propulsion system, several complexities rise up. Typical flow simplifications adopted to speed-up the simulations of the single analysis (hull and propeller separately) lose their validity requiring a more complex solver to tackle the fully-coupled problem. The complexity rises up further when considering a maneuver condition. This aspect increases the computational burden and, consequently, the required time which becomes prohibitive in a preliminary ship design stage. The majority of the simplified methods proposed in literature to include propeller effects, without directly solve the propeller flow, in a high-fidelity viscous solver are not able to provide all the commonly required self-propulsion coefficients. In this work, a new method to enrich the results from a body force based approach is proposed and investigated, with the aim to reduce as much as possible the computational burden without losing any useful result. This procedure is tested for validation on the KCS hull form in self-propulsion and maneuver conditions
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