Alain Texier

Modification of vertical slot fishway flow with a supplementary cylinder

ABSTRACT 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.

Stokes flow inside and around a fluid drop distorted by the presence of a tube wall

Using a quadratic optimisation process to satisfy the boundary conditions, the drag coefficient and the flow patterns inside and outside a fluid drop translating axially in a tube have been determined accurately even when the drop is clearly elongated. Convincing comparisons with experimental results (flow visualizations, velocity and drag measurements) are presented. The effects of the viscosity and density ratios are examined.