Investigation laboratory of the effect of increase of the height of the side wall on the performance of nonlinear weirs

Figures & data

Figure 1. Trapezoidal labyrinth weir (plan view).

Figure 2. Trapezoidal piano-key weir.

Figure 3. The test flume used to conduct the experiments.

Table 1. Test variables.

Q(m^3/s)	Type of weir	Type of parapet wall	Experiment Code
0.01–0.08	PKW	R=6, B́=60	1P
0.01–0.08	PKW	R=4, B́=60	2P
0.01–0.08	PKW	R=2, B́=60	3P
0.01–0.08	PKW	R=6, B́=30	4P
0.01–0.08	PKW	R=4, B́=30	5P
0.01–0.08	PKW	R=2, B́=30	6P
0.01–0.08	PKW	R=0, B́=0	P0
0.01–0.08	TLW	R=6, B́=60	1T
0.01–0.08	TLW	R=4, B́=60	2T
0.01–0.08	TLW	R=2, B́=60	3T
0.01–0.08	TLW	R=6, B́=30	4T
0.01–0.08	TLW	R=4, B́=30	5T
0.01–0.08	TLW	R=2, B́=30	6T
0.01–0.08	TLW	R=0, B́=0	T0

Table 2. Characteristics of the weir models used.

Weir name	No. of cycles	L (cm)	W (cm)	P (cm)	W/P
Piano Key – Base Model	2	272	60	15	4
Trapezoidal – Base Model	2	272	60	15	4

Figure 4. The weir experimented in the test flume. a) 4P model, b) 5P model.

Figure 5. Schematic view of the parapet walls.

Figure 6. Installation of the parapet walls.

Figure 7. The effect on Cd of H_t/P.

Figure 8. The discharge vs hydraulic head diagram.

Figure 9. Effect on Cd of Froude number (Fr).

Figure 10. Effect on Cd of the Weber number.

Figure 11. Comparison between the calculated Cd and the measured Cd for TLW and PKW.

Table

parameter	symbol
discharge coefficient	Cd
sidewall angle	α
slope	S
dynamic viscosity	μ
number of cycles	N
specific discharge or weir discharge per unit spillway channel width ($\mathit{q}=\mathit{Q}/\mathit{W}$)	q
Speed of water	V
water density (assumed to be 998.2 $\mathit{k}\mathit{g}/{\mathit{m}}^3$)	ρ
flume slope	S
distance from the upstream to downstream of the weir	$B$
downstream or inlet key overhang length	Bi
upstream or outlet key overhang length	Bo
sidewalls length	$B{ }^{\mathrm{\prime }}$
weir length	$L$
outlet key length	$L_o$
lateral length of the weir wall	lc
flow discharge	$Q$
water height over the weir	$H$
inlet key width	$W_i$
outlet key width	$W_o$
width of a single cycle	$W_u$
total weir width or flume width	W
height of the inlet/outlet entrance from the PKW crest	$P$
surface tension of water (which is 0.074 at a temperature of 20) $°C$	$L$
gravitational acceleration (9.8 $m/s^2$)	g
sidewalls height	R
total head (sum of velocity and hydrostatic heads)	$H_t$