Labyrinth weirs are considered as non-linear weirs which increase the
discharge capacity for a certain upstream water surface level. In this
study, the effects of dentate and orifice labyrinth weirs on increasing
the discharge capacity in three magnification ratios of (weir length to
flume width, L/W) 2, 3, and 4 was experimentally investigated.
Experiments were conducted in a laboratory flume with length of 15 m,
width of 0.8 m, and height of 1 m in different flow discharges of 10 to
90 lit/s. Totally, 9 physical models with a thickness of 3 mm and a
height of 15 cm were used. The results showed that for L/W= 2 and H/P=
0.2, the discharge coefficient of orifice-dentate weir and dentate weir
are 75.6 and 17.5 percent, respectively, more than the simple labyrinth
weir. However, dent and orifice may lose their efficiency in high heads
and the discharge coefficient will be close to simple labyrinth weir.
The reason for these changes is the flow interference in downstream of
weir. Therefore, for H/P = 0.2, by increasing magnification ratio from 2
to 4 in simple, dentate and orifice-dentate labyrinth weirs, the
discharge coefficient is decreased by 20.8, 32.6, and 44.7 percent,
respectively. This decrease demonstrate that as the weir magnification
increases, the efficiency of orifice and dentate on labyrinth weirs will
extremely decrease and they will act as a simple labyrinth weir.