www.postersessi on.com www.postersession.com www.postersession.com Introduction When a vessel moves in a narrow channel, the increased fluid velocity has a significant effect on the resuspended sediment transport. The vessel-generated wakes (including drawdown and surge waves) have much higher effect on re-suspended sediment than wind waves. It is found that the vessel-induced wakes led to Suspended Sediment Concentrations (SSC) above 400 mg/l which is about 30 times higher than the average background concentration without ships. Even if they are 3D models, they often do not take into account the hydro- sedimentary coupling associated with the passage of ships. A 3D hydrosedimentary model is introduced here. The hydrodynamical model is based on the Reynolds Averaged Navier-Stokes (RANS) equations (implemented in FLUENT13.0) concerning the standard κ − ε model for turbulence processes. The sediment transport model (implemented as user defined subroutine) is based on the mass balance equations for the re-suspended sediment. Ship waves Fig. 4 shows the comparison between the computed and experimental results (CNR. 1997b) of the ship wave profile at probe 2 (Along the line at y = 1.8 m). It shows that the computed drawdown Hd = 0.025 m is 10.7 % lower than the experimental drawdown Hd = 0.028 m. For the secondary waves, the computed maximum wave height Hm =0.022 m, is 18.5 % higher than the measured Hm = 0.027 m (CNR, 1997b). Navigation influence on sediment transport In order to ensure the accuracy of the hydrosedimentary model, the used grid density is bigger than the validated hydrodynamic model. Suspended Particulate Matter (SPM) evolution is supposed to depend on the ship speed and on the wave height. Conclusions References 1. Compagnie National du Rhône (CNR), (1997b). Etude Des ondes de batillage sur modèle physique au 1/30. C753-DLLAB 97-490 2. Ji S.C., Ouahsine A., Smaoui H. & Sergent P. (2012). 3D Numerical Simulation of Convoy-generated Waves in a Restricted Waterway. Journal of Hydrodynamics, Ser. B, 24(3): 420-429. A 3D hydro-sedimentary model is presented to search the relationship between the sediment movement, and the pattern of ship-generated waves around and far away from the ship. The numerical results highlighted the relationships between the maximum SPM and the ship’s speed. They show that the areas of sediment concentration and transport depend mainly on the position and on the ship’s speed in the waterways, on the kinematics of ship-generated waves and on the return flows. In the case with two barges, two additional peaks were generated with reference to the case with only one barge. 3D Numerical simulation of convoy- generated waves and sediment transport in restricted waterways Ouahsine, Abdellatif, UTC, France Ji, Sheng-Cheng, Ji, Sheng-Cheng, UTC, France Sergent, Philippe Sergent, Philippe *, *, CEREMA, France Smaoui, Hassan, Smaoui, Hassan, CEREMA, France Fig. 5 gives the relationship between the SPMmax and the Froude number. We found that the maximum SPM is proportional to the Froude number (or the ship advancing velocities in our case). Three peaks of SPM have been generated by the moving convoy (see Fig. 6). The first peak is produced by the head of the first barge while the second peak and the third peak are induced by the gap between the two barges and the stern of the second barge respectively. Fig. 7 and Fig. 8 show the SPM distribution on the trans- sections and on the symmetry planes respectively, for different values of the blockage coefficient Cb corresponding to canal bottom widths w = 5 m, w = 3 m and w = 2 m for Vb = - 0.6 m/s. * Contact : philippe.sergent@cerema.fr Fig. 1 : Sketch of convoy and channel Fig. 2 : Meshes on hull surfaces and on the boundaries Fig. 3 : Simulated free surface including a barge and a towboat Fig. 4 : Wave profile at probe 2 Comparison with experimental data Fig. 5 : Maximum SPM versus Froude number Fig. 6 : SPM distribution along lines L1, L2, L3 on the symmetry plan (Vb = - 0.6 m/s) Fig. 7 : SPM distribution on trans-section for different blockage coefficients (Cb) Fig. 8 : SPM distribution on the symmetry plane for different blockage coefficients (Cb)