Characterization of hydrodynamics around plates shaped like dragonfly wings as a sediment reduction measure in a sewer system.

Sediment control is a major concern in sewer management. Early studies focused on the parameters affecting the efficiency of existing dredging facilities, and novel long-term sediment reduction measures have not been developed. Superior sediment reduction performance has been demonstrated for plates folded at 25° placed in a pipe. In this study, flushing experiments are carried out to validate the efficacy of using hydrodynamic characteristics to analyze sediment reduction performance. A detached-eddy simulation is performed to characterize the hydrodynamics around various plates shaped like dragonfly wings placed in pipes to enhance sediment reduction performance. Experimental results indicate that the maximum sediment reduction efficiency occurs in the middle section of the plates for both coarse and fine sediment beds, where the flushing thickness is extended by 1.3 cm and 3.2 cm, respectively. However, the sediment reduction efficiency is maximized for mixed sediment beds downstream, where the flushing thickness is extended by 2.4 cm. The results of numerical simulations indicate that compared with conventional sediment reduction measures, the plates produce less detrimental effects on the streamwise velocities near the pipe bottom at the plate front and increase the time-averaged vertical and transverse velocities as well as the overall turbulent kinetic energy. Therefore, the use of plates shaped like dragonfly wings is an effective sediment reduction measure.