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Registros recuperados: 15 | |
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Olagnon, Michel. |
Extreme wave design conditions are of high concern to the offshore industry, especially since many developments are planned in poorly documented areas from a climatological point of view, and since the safety requirements are most stringent. With the availability of a whole decade of satellite observations of sea states, their integration into the state of the art and the remaining difficulties are discussed here. An example is taken with the Iroise Sea, and perspectives are envisionned. |
Tipo: Text |
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Ano: 2002 |
URL: https://archimer.ifremer.fr/doc/00480/59143/61771.pdf |
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Olagnon, Michel; Prevosto, Marc; Ozanne, Philippe. |
This report gives some examples of instrumentation used or anticipated for use on some fixed platforms, aimed at obtaining answers to the questions posed by the heads of petroleum industries concerning the design techniques of these platforms : validity of calculations, guarantee of a normal behaviour of structures until the end of their anticipated serviceable lifetime, detection of serious damage, possibility of extending the serviceable lifetime of structures beyond the lifetime initially anticipated. |
Tipo: Text |
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Ano: 1986 |
URL: https://archimer.ifremer.fr/doc/00480/59128/61756.pdf |
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Olagnon, Michel; Loubersac, Lionel; Aucan, Jerome. |
The present article introduces and defines what are the rogue or freak waves. After an historical reminder on the recent consideration of their existence, several events of waves having struck big or small ships or still the coastline are presented. A paragraph is dedicated to the scientific explanation of the phenomenon and the difference with other phenomenons such tsunamis or tidal bores is clarified. After a reminder of the international mobilization towards a forecast system, a conclusion focuses on events met in New Caledonian waters and analyzes more exactly testimonies related to this type of phenomenon by trying to clarify their causes. |
Tipo: Text |
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Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00186/29724/28142.pdf |
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Alain, Karine; Olagnon, Michel; Desbruyeres, Daniel; Page, Antoine; Barbier, Georges; Juniper, Kim; Querellou, Joel; Cambon-bonavita, Marie-anne. |
As part of an ongoing examination of microbial diversity associated with hydrothermal vent polychaetes of the family Alvinellidae, we undertook a culture-independent molecular analysis of the bacterial assemblage associated with mucous secretions of the Northeastern Pacific vent polychaete Paralvinella palmiformis. Using a molecular 16S rDNA-based phylogenetic approach, clone libraries were constructed from two samples collected from active sulfide edifices in two hydrothermal vent fields. In both cases, clone libraries were largely dominated by epsilon-Proteobacteria. Phylotypes belonging to the Cytophaga-Flavobacteria and to the Verrucomicrobia were also largely represented within the libraries. The remaining sequences were related to the taxonomic... |
Tipo: Text |
Palavras-chave: Proteobacteria; 16S rRNA; Microbial diversity; Phylogeny; Hydrothermal vent; Paralvinella palmiformis. |
Ano: 2002 |
URL: https://archimer.ifremer.fr/doc/2002/publication-661.pdf |
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Olagnon, Michel; Guede, Zakoua. |
This paper provides theoretical formulas to calculate conservative estimates of the rainflow fatigue damage from the spectral parameters for spectra composed of the combination of one or several narrow-band low-frequency loads and a higher frequency one, such as are often encountered with moored marine structures. With respect to the semi-empirical formulas that have been proposed by other authors, those presented here are theoretically constructed from the mathematical definition of rainflow and from the statistical properties of Gaussian processes. (C) 2008 Elsevier Ltd. All rights reserved. |
Tipo: Text |
Palavras-chave: Random loading; Rainflow; Spectral fatigue; Fatigue. |
Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4197.pdf |
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Olagnon, Michel; Becq, Françoise; Charriez, Patrick. |
To design offshore structures, to prepare operations at sea and unusual transportations on marine routes, to assess safety levels with respect to marine climate, one needs practical data describing the wave, wind and current conditions that may occur. This essential information is unfortunately very seldom readily available exactly for the geographical area of interest. Where to look for it, how to evaluate and choose amongst what one may find, how to get aware of its adequation and drawbacks for the projected use, whom to call for help, as many questions to which this report is expected to bring some answers. Engineers in charge of coastal or offshore projects, logistics managers implied in sea transportations, underwriters, planners for shore equipments... |
Tipo: Text |
Palavras-chave: Offshore engineering; Water waves; Ocean currents; Meteorological data. |
Ano: 1992 |
URL: http://archimer.ifremer.fr/doc/1992/rapport-988.pdf |
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Olagnon, Michel; Kpogo-nuwoklo, Komlan; Guede, Zakoua. |
Accurate estimation of long-term sea conditions is a major issue for the design of coastal and offshore structures, for the preparation of marine operations, and for other applications such as marine energy, and coastal erosion. It requires, on the one hand, proper parametric models of the sea state spectra and the statistics of the parameters, and on the other hand, representations of their time evolutions. In some locations such as West Africa, sea conditions are complex with wave spectra showing many well separated peaks corresponding to several swells and wind sea. The present study focuses on swell at a West Africa location. First, a time-consistent triangular model is assessed for the spectral shapes of the swell components. Then statistical analysis... |
Tipo: Text |
Palavras-chave: Joint probabilities; Metocean time-series; Swell spectral models; Ocean wave climate; Event tracking; Offshore fatigue design. |
Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00156/26695/24761.pdf |
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Olagnon, Michel. |
Designers and naval architects can legitimately feel concerned as to whether freak waves, of unexpected severity, are correctly accounted for in current design practices and regulations. We describe here the main findings related to that phenomenon, achieved mainly during the last decade by analysis of field data, theoretical developments and wave flume experiments. It appears that conventional design methods are not actually challenged given the reliability levels required at present. Nevertheless, freak or rogue waves remain a danger for operations and work at sea. The hypotheses for their generating mechanisms have still not been validated in actual seas, and it is thus not possible to forecast either precisely any increase in their risk of occurrence... |
Tipo: Text |
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Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00116/22677/20412.pdf |
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Guede, Zakoua; Olagnon, Michel; Pineau, Hélène. |
The purpose of this study is to validate the use of the so-called Iterative Component Addition (ICA) formulas for the assessment of fatigue damage of marine structures subjected to complex (multimodal) wave loading conditions, as prevail in West Africa areas where the sea states are usually described as combinations of three wave systems (e.g. main swell, secondary swell and wind sea). In this context, operators specifications require to consider a very large set of fatigue loading cases, which lead to excessive computation times if the conventional procedure is used for fatigue assessment. The use of the ICA formulas is expected to simplify the evaluation of the damage and to allow a drastic reduction of computation time, keeping a slight level of... |
Tipo: Text |
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Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00484/59556/62540.pdf |
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Olagnon, Michel; Prevosto, Marc; Van Iseghem, Sylvie; Ewans, Kevin; Forristall, George Z.. |
The OGP Workshop on the Metocean and Engineering Aspects of Floating Systems which was held at St. Albans in April 2001 identified better discrimination of the low frequency end of the wave spectrum as one of the most pressing problems for the design and analysis of floating systems. The responses of many floating systems have proven to be very sensitive not only to the amplitude and frequency of the swell, but also to the details of the shape of the swell peak in the spectrum. There has been relatively little serious study of the low frequency end of the wave spectrum compared to the effort that has gone into the study of the high frequency tail of the spectrum. Much of the present interest in swell comes from the active deep water developments taking... |
Tipo: Text |
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Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/00114/22537/20216.pdf |
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Registros recuperados: 15 | |
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