Discharge Efficiency of Reservoir-Application-Specific Labyrinth Weirs

Published labyrinth weir design methods, which have primarily been developed on the basis of labyrinth weir test data from laboratory flumes, are specific to in-channel labyrinth weir applications in which the approach flow is oriented normal to the weir axis. Consequently, some uncertainty exists regarding the hydraulic performance of labyrinth weir configurations that are specific to reservoir applications (i.e., projecting, flush, rounded inlet, and arced labyrinth weirs). The discharge efficiency, as characterized by the weir discharge coefficient, of laboratory-scale projecting, flush, rounded inlet, and arced labyrinth weirs with 12 degree sidewall angles, were evaluated as a function of $H_T/P$ and compared with in-channel labyrinth weir discharge efficiencies. The arced labyrinth weir configuration had a higher discharge efficiency ($\sim 5–11\%$ higher than an in-channel labyrinth weir orientation). In general, the projecting, flush, and rounded inlet orientations were less efficient than the in-channel labyrinth weir configuration.