Supercritical flow around an emerged cylinder

Thomas Ducrocq, Ludovic Cassan, Helène Roux, Jacques Chorda

Thursday 2 july 2015

9:30 - 9:45h at Amazon (level 1)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 10B. Engineering - River

To ensure the ecological continuity and the free circulation of migratory fishes, facilities have to be built in or around obstacles as dams. These facilities are called fishways and the focus is made, in this study, on "natural fishways" which are high slopes channels composed of blocks rows arranged in staggered. The aim of the study is to understand the flow structure in this kind of fishpasses in order to better design them and improve their passability. The first approach is achieved on a single block to validate the model. Experiments are conducted on a laboratory flume and computations are carried out with the same geometry. The tested configuration is an emerged cylinder with a diameter of 4cm, the energy slope of the flow is of 0.34%. The software OpenFOAM which enables to do massively parallel computing is used for the simulations. The VOF model is used to track the free surface and two turbulence models are tested. In the experiment, particles are injected in the flow in order to reconstruct the velocity field by particle tracking, using a high speed camera. The objective is the comparison of the free surface flow between experiments and simulation results at relative large Froude number (F=0.54). Finally, the results show a good agreement between the experiments and the simulations. The perspective is the simulation of a full fishpass.