Marilyne Luck

Testing models for predicting the behaviour of radionuclides in aquatic systems

The paper describes the main results of the international EMRAS model testing exercise for radionuclide transport in watershed-river and estuarine systems. The exercises included the following scenarios: multi-point source of (3)H discharge into the Loire River (France), radioactive contamination of the Dnieper-Southern Boug estuary (Ukraine), remobilisation of radionuclide contamination from the Pripyat River floodplain (Ukraine) following the Chernobyl accident, release of radionuclides into the Techa River (Russia) and behaviour of (226)Ra in the Huelva estuary (Spain).

Efforts dus aux vagues sur un cylindre vertical en zone côtière : Etude expérimentale et méthodes de prédiction

ABSTRACT Wave-induced loadings acting on a monopile structure were investigated by experimental tests on a vertical cylinder in a wave flume with a sloping bottom, considering non-breaking, breaking and broken wave conditions. Measured forces were compared to numerical predictions obtained by applying Morison formula and by using different methods to compute the wave kinematics. This comparison highlights the need for accurate prediction methods for wave kinematics of shoaling and breaking waves. Indeed the linear wave theory often leads to significant underestimation of the measured forces. Using advanced stream function methods or the modified transfer function method, this under-prediction is significantly reduced, but additional work is needed to predict the impulsive force due to breaking on the structure better.

Prédiction de la cinématique de houle en zone de déferlement

ABSTRACT This paper deals with the prediction of wave kinematics in the nearshore and coastal zones, where bottom variations strongly affect wave propagation and their characteristics. Measurements of wave kinematics have been performed near the bottom for a large number of shoaling and breaking wave conditions, and also over the water column inside the breaking zone for three particular conditions. These experimental data serves to evaluate and compare several numerical methods, including Flat Bottom Theories (FBT), Sloping Bottom Methods (SBM) and Transfer Function Methods (TFM). It is shown that advanced TFM give the best predictions for wave kinematics, provided that the local free surface elevation signal is available. Particular SBM may also produce reliable prediction for the case of plane slope from a limited number of wave parameters, whereas FBT should not be used in the coastal zone.