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

ABSTRACT

Labyrinth 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

Keywords:

• Control structure
• hydraulic structure design & management
• laboratory study
• labyrinth weir
• sedimentation
• turbulence–sediment interaction

Acknowledgements

The authors thank Udo Pfrommer who provided support and equipment and enabled a smooth running of the lab. Dr Sina Wunder and Prof. Dr. Olivier Eiff, both from Karlsruhe Institute of Technolgy (KIT), supervised the Master’s thesis of Jakob Herbst and the Bachelor’s Thesis of Alexander Leitz and gave many valuable comments.