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This work presents an experimental study of the effects of finite water depth on the waves generated by a ship in a towing tank. The wakes of two hull forms representative of maritime and river ships are measured for both deep water and shallow water configurations and for several Froude numbers. The free surface deformations are measured with an optical stereo-correlation measurement method to access a full and detailed reconstruction of the wave fields. The spatial resolution of the reconstructed wakes allows us to perform a spectral analysis of the waves generated by the ships and to decompose them into a near-field hydrodynamic response and a far-field undulatory component. First, the spectral analysis method is presented and the effects of finite water depth on a theoretical point of view are studied. The analysis of subcritical, trans-critical, and supercritical ship wakes in both real space and spectral space highlights the effects of the finite water depth, of the ship speed, and of the hull shape on the energy distribution in the ship wakes through these different regimes.

The paper reports on the experimental results of a vertical slot fishway (VSF) study. Particle image velocimetry and Acoustic Doppler Velocimetry were used to estimate the effects of a supplementary cylinder, appropriately positioned inside existing VSFs, on the hydraulic parameters and the instantaneous flow patterns. Special attention was paid to the analysis of the spatial flow distribution and to the instantaneous flow dynamics initiated by the addition of a cylinder. Modifications of velocity amplitudes, flow fluctuations and vorticity values were quantified for two dimensions of VSF. The contribution of a supplementary cylinder has been quantified in order to "smooth" the effects of turbulence and to facilitate the passage of the largest number of fish irrespective of their size or swimming capacity. The results provided insights on the control of the fishway turbulence, which might help engineers to develop effective systems for the passage of fish with low swimming capabilities.

International audienceThe kinematics of hydrodynamic turbulent flows developed in vertical slot fishways (VSF) was studied in detail in flow patterns not yet published to date for the purposes of modifying existing devices and to allow for the passage of all fishes, particularly the smaller species. A transparent device based on the typical prototype dimensions of VSF in France was constructed for the experiment. The velocity measurements were carried out by Particle Image Velocimetry (PIV). These measurements were used to determine the various kinematics parameters characterizing the flow. From the dimensions and slope of the fishway, two flow topologies highlighting the swirling pattern were proposed. The method of Proper Orthogonal Decomposition (POD) was used to undertake unsteady and energetic analyses to characterize the main phases of flow evolution that fish passing through the passage may encounter

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This paper details the spectral analysis of the waves generated from an experimental study of the water surface elevation around a ship model in a towing tank. The wave pattern is measured with accurate optical methods in deep-water conditions for various Froude numbers. These optical methods allow the entire wave field around the model with a high spatial resolution to be obtained. The quality of the measured surface elevation around the ship model enables us to perform a spectral analysis of the waves generated by a ship. To validate this approach, the experimental spectrum is compared to the fundamental theoretical dispersion relation of the waves generated by a moving perturbation in calm deep water. In a second step, a fundamental decomposition of the wave system is achieved, from which the contribution of the near field, the local flow disturbance, and the contribution of the far field that corresponds to the Kelvin wake system are computed. In addition, the experimental extraction of the dispersion relation provides an estimate of the angle of the cone of the Kelvin wake in the spectral space.

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