Influence of Log Jam Visor on Flow Rate at a Standard Spillway

Flood events may generate large amounts of floating debris. Especially large wood debris may clog up or dramatically decrease the spillway capacity. For safety reasons, it is crucial to find a mitigation measure that conserves the discharge and stops the floating debris into the lake at the upstream dam. Furthermore, a visor may be proposed to avoid the clogging of the spillway. The main goal of the present study is to test a wide range of note-worthy parameters, namely: the visor position, the spillway head, the basin head, the wood characteristics and the main visor slope. For that purpose, VOF calculations carried out with the software Flow 3D were coupled with a home-made Python automation code in order to create and run automatically around 1,300 simulations. A first run of simulations was performed in 2D to efficiently determine the most suitable location of the structure. The visor was mimicked by a square porous medium. Then a full 3D model was used to further investigate the influence on the discharge drop of the rack. We added a finite number of floating logs randomly introduced in the domain upstream from the visor. Both 2D and 3D numerical results were challenged by physical experimentations available in literature. According to results, numerical models help us to find out the best location where the discharge capacity of the standard spillway is preserved despite the debris. Secondly, it provides an accurate understanding of the different clogging processes depending on log types and flow conditions.