3D computational modeling of the Galaube Dam spillway

Résumé En

A revision of the hydrology study for the Galaube dam catchment area has been made as part of the dam safety report. This study highlights an increase of the design flood. A 3D CFD free surface hydraulics model of the Galaube dam is built with ANSYS CFX in order to verify the discharge capacity for the new design flood. The 3D CFD model is validated on two elements : the results of the initial studies and the model’s sensitivity on the roughness coefficients and the mesh size. The different attempts on the model’s sensitivity don’t lead to important modifications of the spillway rating curve. Moreover, it appears that, in a range of flow, the rating curve calculated with the 3D computational model is smaller than the rating curve obtained in the initial studies. This reduction is due to a drowning of the weir. This phenomenon is highlighted with the 3D CFD model. Furthermore, the model permits the identification of the limit flow rate before the saturation of the spillway and the representation of the transition in flow characteristics. Otherwise, the results are used to define some works to insure the dam safety : the dam freeboard and the wave wall safety are checked, and the height of the spillway training wall is increased.