Hydraulic Resistance of Emergent Macroroughness at Large Froude Numbers: Design of Nature-Like Fishpasses

Ludovic Cassan (1) , Tien Tran Dung (2) , Dominique Courret (3) , Pascale Laurens (1) , Denis Dartus (1)

1 IMFT - Institut de mécanique des fluides de Toulouse
2 Thuy Loi University - TLU (VIETNAM)
3 ONEMA - Office national de l'eau et des milieux aquatiques

The mean flow in a nature-like fishpass can be highly modified by the Froude number. It is important to understand this evolution to correctly design the structure. The studied configuration is an emergent staggered arrangement of obstacles. The hydraulic resistance of a fishpass is experimentally investigated that depends on several geometric parameters: block shape, ramp slope, block density, and bed roughness. An analytical model based on the balance momentum allows one to quantify the influence of each hydraulic parameter. The bed roughness has a weak influence, whereas the block shape and the Froude number are significant. The variation of the drag coefficient was analyzed to improve the stage-discharge relationship. To this end, a correlation with the block diameter and water level is proposed. The maximal velocity reached in the fishpass can also be estimated. These results have to be compared with the fish swimming ability to assess the fishpass passability.

Mots clés: Nature-like fishpass; Flow resistance; High Froude number; Emergent block; Drag coefficient

Domaines: Hydrologie; Milieux fluides et réactifs

Ludovic Cassan, Tien Tran Dung, Dominique Courret, Pascale Laurens, Denis Dartus. Hydraulic Resistance of Emergent Macroroughness at Large Froude Numbers: Design of Nature-Like Fishpasses. Journal of Hydraulic Engineering, 2014, vol. 140 (n° 9), pp. 1-9. ⟨10.1061/(ASCE)HY.1943-7900.0000910⟩. ⟨hal-01166268⟩