


Registros recuperados: 21  


Guanche Garcia, Yanira; Prevosto, Marc; Maisondieu, Christophe; Bulteau, Thomas; Paris, François. 
The knowledge of extreme events of environmental variables is an issue of increasing concern to the scientific community. Within the branch of coastal and ocean engineering there are many fields of application where an accurate estimation of long term return period events is needed, i.e. coastal defenses design, coastal flooding management, estimation of changes of the littoral morphology, offshore and onshore renewable energy devices design, etc. But not only the engineers are concerned by extreme events; biological communities in the open sea and estuarine systems are also exposed to extreme events that may affect its natural development (i.e. extreme sea levels in estuarine environments could raze fields of plants not able to deal with salt in just a... 
Tipo: Text 

Ano: 2015 
URL: http://archimer.ifremer.fr/doc/00378/48967/49370.pdf 
 

 


Venugopal, Vengatesan; Davey, Thomas; Smith, Helen; Smith, George; Holmes, Brian; Barrett, Sean; Prevosto, Marc; Maisondieu, Christophe; Cavalieri, Luigi; Bertotti, Luciana; Lawrence, John; Girard, Francoise. 
This report gives guidance relevant to the resource assessment of sites considered for the deployment of wave and tidal energy converters. Areas considered include: instrumentation and measurement; techniques and requirements for wave and tidal parameterisation; wavecurrent interaction; spatial and temporal variation. A number of case studies are also included examining several European sites. 
Tipo: Text 

Ano: 2011 
URL: http://archimer.ifremer.fr/doc/00250/36152/34706.pdf 
 


Paillard, Michel; Prevosto, Marc; Barstow, Sf; Soares, Cg. 
The MAST II WAVEMOD Project aimed at improving stochastic modelling of ocean waves and currents in coastal waters. In order to supplement existing data, two measurement campaigns were carried our, one on the Atlantic coast of Portugal, and, secondly, on the northern coast of Crete in the Mediterranean. The Portuguese measurements covered 7 months during winter 19931994, while off Crete, measurements started early in February 1994 and continued for 10 months, In both sites, two directional Waveriders and one nondirectional Waverider were deployed along a transect our from the coast in water depths between 10 and 100 m. In addition, the Mediterranean site also incorporated measurements of mean current velocities. Available satellite data were analysed to... 
Tipo: Text 
Palavraschave: Waves; Currents; Portugal; Greece. 
Ano: 2000 
URL: https://archimer.ifremer.fr/doc/00000/10506/66722.pdf 
 


Prevosto, Marc; Soulard, Thomas. 
When Newman's approximation is used to calculate the low frequency part of the nonlinear transfer between the waves and the forces on an LNG carrier, the CPU time to make the time series reconstruction of wave loads is a small part of the total. However, using full QTFmatrices increases the required work by a factor equal to the number of wave components in the sea states and the total simulation time can be increased by 5 or 10. Moreover, if we consider the multidirectional sea, the double summation becomes a quadruple summation at second order which is extremely timeconsuming. There is a way to accelerate this computation by making an algebraic or system approximation of the QTF. The aim of this report is to present the solutions, the problems and the... 
Tipo: Text 

Ano: 2007 
URL: http://archimer.ifremer.fr/doc/00239/34986/33520.pdf 
 


Klinghammer, Christian; Prevosto, Marc; Le Boulluec, Marc; Perignon, Yves. 
Up to this day, design recommendations or practices for floating structures, such as DNVs RPC205 and F205 for example, do not account for the existence of low frequency free Infragravity (IG) waves. These are lowfrequency water waves which represent an additional excitation for (moored) floating structures. In this study, the influence of free IG waves on moored floating structures response is investigated and compared to secondorder lowfrequency wave forces, as the standard low frequency excitation, for two selected important free IG events in 2013 and 2014 at the SEMREV (Site d'Experimentation En Mer  Récupération de l'Energie des Vagues) test site near Le Croisic, PaysdelaLoire, France. The wave forces and motion response for two example... 
Tipo: Text 

Ano: 2015 
URL: http://archimer.ifremer.fr/doc/00384/49584/50094.pdf 
 


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 

Ano: 1986 
URL: https://archimer.ifremer.fr/doc/00480/59128/61756.pdf 
 


Raillard, Nicolas; Prevosto, Marc; Ailliot, Pierre. 
Many records in environmental science exhibit asymmetries: for example in shallow water and with variable bathymetry, the sea wave time series shows front–back asymmetries and different shapes for crests and troughs. In such situation, numerical models are available but their computational cost and complexity are high. A stochastic process aimed at modeling such asymmetries has recently been proposed, the Laplace moving average process, which consists in applying a linear filter on a nonGaussian noise built using the generalized Laplace distribution. The objective is to propose a new nonparametric estimator for the kernel involved in the definition of this process. Results based on a comprehensive numerical study will be shown in order to evaluate the... 
Tipo: Text 
Palavraschave: Laplace moving average; Nonlinear time series; FIR estimation; Splines; Highorder spectrum; Asymmetries. 
Ano: 2015 
URL: http://archimer.ifremer.fr/doc/00201/31189/29588.pdf 
 

 

 

 


Prevosto, Marc; Le Louarne, Jeanfranois; Guede, Zakoua. 
In this study we discuss various methods to assess the statistics of extreme response of a floating structure subjected to random waves. This issue is of great importance in the case of low frequency motion of floating bodies in shallow water. Those methods are based on the evaluation of the level crossing rate, which is easily related to the extreme value statistics for stationary random processes and large levels. Four main methods are considered, namely the Rice formula with either a Gaussian assumption or an approximation of the joint distribution of the response and its first derivative by a projection method; the Breitung's formula; the Hagberg's approaches using either an asymptotic expansion or a MonteCarlo integration and finally the time domain... 
Tipo: Text 
Palavraschave: Low frequency motion; Shallow water; Second order wave loading; Crossing rate; Extreme response. 
Ano: 2007 
URL: http://archimer.ifremer.fr/doc/2007/acte6329.pdf 
 


Prevosto, Marc. 
The statistics of the elevation and kinematics of waves in real seas are very rarely accessible from insitu measurements which induced very high costs. An alternative to the actual waves observation is to derive from the spectral climatology of waves, completed with other environmental data like the wind and the current, the statistics of the individual waves. But this requires accurate models of irregular gravity waves which take into account all the main nonlinearities and interactions with the local wind, current and bathymetry. In a first step, methodologies have been based on second order irregular wave 3D models and have supplied the engineers with new better accurate models of statistics of wave crests. These models do not include yet the complex... 
Tipo: Text 

Ano: 2000 
URL: http://archimer.ifremer.fr/doc/00116/22715/20457.pdf 
 


Monbet, Valérie; Ailliot, P; Prevosto, Marc. 
The knowledge of sea state and wind conditions is of central importance for many offshore and nearshore operations. In this paper, we make a complete survey of stochastic models for sea state and wind time series. We begin with methods based on Gaussian processes, then nonparametric resampling methods for time series are introduced followed by various parametric models. We also propose an original statistical method, based on Monte Carlo goodnessoffit tests, for model validation and comparison and this method is illustrated on an example of multivariate sea state time series. (C) 2006 Elsevier Ltd. All rights reserved. 
Tipo: Text 
Palavraschave: Model validation; Simulation; Nonlinear time series; Wind; Sea state. 
Ano: 2007 
URL: http://archimer.ifremer.fr/doc/2007/publication2679.pdf 
 


Puillat, Ingrid; Prevosto, Marc; Mercier, Herle; Thomas, S.. 
In our time emerged the idea of a major environmental degradation, at both local and global scales, in the face of the recurrent human pollution. Consequently in the sake of a sustainable humanity development, of the ethic and of the ecology, the protection and the monitoring of our environment have become a major stake. Many scientific and technical tools contributed to improve the environmental knowledge, as helped remote and in situ observations, and forecast modeling. In situ environmental sensor systems have been designed to be increasingly sustainable even in a hostile environment such as the deep ocean. In a similar way, the infrastructures hosting those sensors are now thought and built to be permanent. In marine sciences these considerations gave... 
Tipo: Text 
Palavraschave: Time series; Marine data; Signal processing; Statistics. 
Ano: 2014 
URL: http://archimer.ifremer.fr/doc/00161/27259/25468.pdf 
 


Prevosto, Marc; Van Iseghem, Sylvie; Moreau, Benjamin; Forristall, George Z.. 
Despite its great theoretical and practical importance, the statistical distribution of crest heights has remained poorly known. The uncertainties are due to difficulties both with the theory, where nonlinear effects must be accurately modeled, and with measurements, where different sensors appear to give different results. In response to this uncertainty, the Wave Crest Sensor Intercomparison Study (WACSIS) was formed as a Joint Industry Project in order to provide data for comparing the response of wave sensors and for comparing theories of crest height distributions with the measurements. The key to the WACSIS experiment was to place all of the popular sensors on the same platform located where they were likely to experience large waves in one season.... 
Tipo: Text 

Ano: 2001 
URL: http://archimer.ifremer.fr/doc/00117/22841/20651.pdf 
 


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 

Ano: 2004 
URL: http://archimer.ifremer.fr/doc/00114/22537/20216.pdf 
 


Filipot, Jeanfrancois; Prevosto, Marc; Maisondieu, Christophe; Le Boulluec, Marc; Thomson, Jim. 
This work presents the analysis of wave and turbulence measurements collected at a tidal energy site. A new method is introduced to produce more consistent and rigorous estimations of the velocity fluctuations power spectral densities. An analytical function is further proposed to fit the observed spectra and could be input to the numerical models predicting power production and structural loading on tidal turbines. Another new approach is developed to correct for the effect of the Doppler noise on the high frequencies power spectral densities. The analysis of velocity time series combining wave and turbulent contributions demonstrates that the turbulent motions are coherent throughout the water column, rendering the wave coherencebased methods not... 
Tipo: Text 

Ano: 2015 
URL: http://archimer.ifremer.fr/doc/00254/36537/35074.pdf 
 

 
Registros recuperados: 21  


