Sedimentation at labyrinth weirs – an experimental study of the self-cleaning process

ABSTRACTLabyrinth weirs are passive flow control structures. It is assumed they hold back more sediment compared to movable weirs. Only a few model tests have been conducted for specific prototypes up to now. Therefore, systematic experimental tests were performed on a physical model with a rectangular and a trapezoidal labyrinth weir. Four sediments were tested under various flow conditions: fine sand, fine gravel, medium grained gravel and polystyrene granules. The results confirmed the self-cleaning ability of labyrinth weirs. Furthermore, the model tests show that the densimetric Froude number is the dominant parameter and has a significant effect on the scouring mechanism. It can be seen that self-cleaning begins at a rectangular labyrinth weir at lower discharges compared to a trapezoidal labyrinth weir. Finally, the self-cleaning process can be described and a threshold can be determined to predict scouring in dependence of geometry, discharge and sediment properties