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Compiègne, France

Gallen R.,CETMEF | Gallen R.,UniverSud | Cord A.,UniverSud | Hautiere N.,University Paris Est Creteil | Aubert D.,University Paris Est Creteil
IEEE Intelligent Vehicles Symposium, Proceedings | Year: 2011

Compared to daytime, a larger proportion of accident happens during nighttime. The altered visibility of the road scene for the drivers may partially explain this situation. The latter becomes worse in fog presence. In this paper, two camera-based methods are proposed to detect the presence of night fog in images grabbed by in-vehicle multipurpose cameras. They rely on the visual effects of night fog. A first approach can assess the presence of fog around the vehicle thanks to the detection of the backscattered veil induced by the vehicle ego lights. It aims at detecting fog when the vehicle is alone in absence of exterior public lighting. A second approach can assess the presence of fog thanks to the detection of halos around light sources in the vehicle environment. It aims at detecting fog in presence of road traffic or public lighting. Both methods are presented and illustrated with actual images of fog. Their complementarity makes it possible to envision a complete night fog detection system. There are numerous applications for such a system: automation or adaptation of vehicle lights, contextual speed computation and reliability improvement for camera-based systems. © 2011 IEEE. Source

Ji S.C.,CNRS Roberval Laboratory (Mechanical Research Unit) | Ouahsine A.,CNRS Roberval Laboratory (Mechanical Research Unit) | Smaoui H.,CNRS Roberval Laboratory (Mechanical Research Unit) | Sergent P.,CETMEF
Journal of Hydrodynamics | Year: 2012

We consider waves generated by the passing of convoys in a restricted waterway. The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy, such as the speed and the hull geometry. The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown. Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k - ε model for turbulent processes. The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rhône (CNR). © 2012 Publishing House for Journal of Hydrodynamics. Source

Ji S.,CNRS Roberval Laboratory (Mechanical Research Unit) | Ouahsine A.,CNRS Roberval Laboratory (Mechanical Research Unit) | Smaoui H.,Compiegne University of Technology | Sergent P.,CETMEF
International Journal of Sediment Research | Year: 2014

Ship-generated waves and return currents are capable of re-suspending significant quantities of bottom and bank sediments. However, most of the previous studies done on the subject do not show how and where sediment is re-suspended by the wakes and the directions of net transport. In this paper, a 3D numerical model based on hydro-sedimentary coupling is presented to search the relationship between the sediment movement, and the pattern of ship-generated waves around and far away from the vessel and the return currents around the ships. The hydrodynamic model is based on 3D Navier-Stokes equations including the standard k-ε model for turbulence processes, and the sediment transport model is based on a 3D equation for the re-suspended sediment transport. The computation results show that the areas of sediment concentration and transport (whether by resuspension or by the bedload) depend mainly on the position, the speed of the ship in the waterways, the kinematics of ship-generated waves and on the return flows. Thus, a map of sediment distribution and the modes of sediment transport generated by the passage of the ship are presented. © 2014 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research. Source

Goutx D.,Meteo - France | Baraer F.,Meteo - France | Roche A.,CETMEF | Jan G.,SHOM
Houille Blanche | Year: 2014

Risk studies of coastline flooding strive to define extreme values for sea level and the surf and then combine them to determine a threat index for the seaboard. However, these phenomenona are often generated by the same type of weather event: the storms. Meteo-France, the Cetmef and the Shom got together to study the storms threatening the coast of Brittany and to determine the extreme events the associated hydrodynamic parameters of which would allow to study the risk of coastline flooding. By combining archives and re-analysis (ERA-Intérim), each storm is documented; then a typology is implemented to establish within each cluster, which elements are the most representative. The Arpege model enables us to restore the most typical historical storms, then the Ensemble Prevision supplies data on fictitious but plausible storms that can be afterwards combined with unfavourable tide conditions. This method which enables us to study plausible extreme events not yet revealed to us, creates the problem of the likelihood of these fictitious events. It is nonetheless an innovative technique, relevant for the understanding of extreme events so that the strategies used to adapt our shorelines, as it is demanded by the 2007/60/CE European Directive in the case of extreme events, could be assessed. © 2014 Société Hydrotechnique de France. Source

Dupray S.,CETMEF | Dupray S.,HR Wallingford | Gamst K.,CIRIA | Robertshaw G.,Halcrow Group Ltd. | And 2 more authors.
Coasts, Marine Structures and Breakwaters: Adapting to Change - Proceedings of the 9th International Conference | Year: 2010

The findings of the research summarised above will be available in the second half of 2009 in the form of a 'Manual on the use of concrete in the maritime environment'. The report will be published by CIRIA. It will also be translated and published in French by CETMEF. Source

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