Validation of a 1D Simplified Model of Gironde Estuary Based on a Database of TELEMAC Simulations

Hydrodynamic

Trim optimisation in waves

The trim optimisation is nowadays a common practice for all ship owners. Reduction o fuel consumption and improvement of ship energy efficiency concern all sectors of the maritime industry. The trim optimisation consists in finding the best trim angle with regards to the lowest power - i.e. fuel consumption - for a given operating condition (loading condition and speed). Although the operational efficiency of trim optimisation based on calm water resistance computations databases could be proven at sea, it is well known that added resistance due to wave can significantly impact fuel consumption. The increase of cluster computing power make it today possible to evaluate the added resistance in waves using state of the art free surface RANSE solvers. This study of the optimal trim depending on the sea- states show that taking into account the waves could have a significant impact on the optimal trim that have been identify on still water. Although the optimal trim angle trends are the same on still water and in waves for low sea-states, for highest sea-states the trends can be the perfect opposite. This study shows that the optimal trim mainly depends on the draft and the sea-state. The speed seems to have an effect on the gains / losses amplitude but not on the best trim value. The in waves databases will enable operators to predict their ship efficiency with better accuracy, taking into account weather predictions. The trim needs to be therefore adapted regularly depending on the weather conditions the ship encounter during her voyage

Simulations numériques de l'évolution des fonds et effet du mélange turbulent sur le transport sédimentaire:Application au remplissage d'une fosse d'extraction

International audienceLe profil linéaire de longueur de mlange $l_{m}=\kappa z$ classiquement utilisé, ne permet pas d'obtenir le profil de vitesse logarithmique observ\é expérimentalement, et sa validité est limitée aux domaines de faible rugosité (conditions aux limites du type 'fond lisse'). Dans ce travail, nous proposons trois types de profils de longueur de mélange $l_{m}(z)$ ainsi que les profiles de vitesses de mélange associés. Les résultats obtenus, sont testés sur des cas académiques et comparés aux résultats expérimentaux de remplissage d'une fosse d'extraction issus des essais présentés dans le projet Européen Sandpit

The hydrodynamic, sea-state and infrastructures platform developed by Saint-Venant Hydraulics Laboratory and Cerema: a special focus on the TELEMAC2D surge levels numerical model of the Atlantic Ocean, the Channel and the North Sea

Water Qualit

High quality factor nitride-based optical cavities: microdisks with embedded GaN/Al(Ga)N quantum dots

We compare the quality factor values of the whispery gallery modes of microdisks incorporating GaN quantum dots (QDs) grown on AlN and AlGaN barriers by performing room temperature photoluminescence (PL) spectroscopy. The PL measurements show a large number of high Q factor (Q) resonant modes on the whole spectrum which allows us to identify the different radial mode families and to compare them with simulations. We report a considerable improvement of the Q factor which reflect the etching quality and the relatively low cavity loss by inserting QDs into the cavity. GaN/AlN QDs based microdisks show very high Q values (Q > 7000) whereas the Q factor is only up to 2000 in microdisks embedding QDs grown on AlGaN barrier layer. We attribute this difference to the lower absorption below bandgap for AlN barrier layers at the energies of our experimental investigation

3D numerical simulation of ship resistance in restricted waterways including ship squat effects

This study focuses on the effect of waterway restriction on ship resistance of an inland vessel. A 3D numerical model allowing to predict ship resistance in confined waters by taking ship sinkage into account has been developed. The numerical results are compared to experimental data from towing tank test and the influence of taking ship sinkage into account on the prediction error is studied