LAUSR

With an increase of the length of a crest in a given width, labyrinth weirs lead to an increase in flow transition capacity over the weir. This study was performed on a laboratory flume with a length of 12.5 m, width of 0.3 m and a height of 0.4 m, using triangular labyrinth weirs (with and without slots), each having single‐ and two‐cycle models. First, their hydraulic performance was examined, and then it was compared with that of a piano key weir (single‐cycle, two‐cycle). The results showed that the increase in crest length through a slot in single‐ and two‐cycle weirs cannot be an effective factor. The presence of a slot in single‐ and two‐cycle triangular weirs led to a decrease in the discharge coefficient of these weirs up to 35 and 33% respectively, compared to weirs without any slot. This is due to energy loss, local submergence and flow interference in the nose slot even at low flows. However, the flow's index weir (triangular weir slot, one slot) compared to single‐ and two‐cycle piano key weirs dropped by 40 and 26% respectively.