Mar. 6,1916 
Flow through Weir Notches 
1095 
Table XIV .—Velocities of approach {in feet per second) and percentages of increase in 
discharges through Cipolletti notches caused by different bottom and end contractions 
HEAD, 0.6 FOOT 
End 
con¬ 
trac¬ 
tions. 
i-foot notch. 
iM-foot notch. 
2-foot notch. 
3-foot notch. 
4-foot notch. 
Bottom 
contrac¬ 
tion. 
Veloc¬ 
ity of 
ap¬ 
proach. 
In¬ 
crease 
of dis¬ 
charge. 
Veloo 
ity of 
ap¬ 
proach. 
In¬ 
crease 
of dis¬ 
charge. 
Veloc¬ 
ity of 
ap¬ 
proach. 
In¬ 
crease 
of dis¬ 
charge. 
Veloc¬ 
ity of 
ap¬ 
proach. 
In¬ 
crease 
of dis¬ 
charge. 
Veloc¬ 
ity of 
ap¬ 
proach. 
In¬ 
crease 
of dis¬ 
charge. 
Feet. 
Feet. 
f 2.0 
0.158 
Per ct. 
0.84 
0.207 
Per ct. 
1.02 
0.251 
Per ct. 
1.21 
0.321 
Per ct. 
i -45 
0-373 
Per ct. 
1.61 
1 X . 
1.5 
. 196 
1.11 
•255 
1-38 
• 3°4 
1.60 
•377 
1-95 
.429 
2.19 
l 1.0 
. 260 
1.70 
•329 
2.08 
.381 
2-36 
•454 
2. 77 
•504 
3.02 
•5 
.400 
3-32 
.469 
3-83 
.518 
4.20 
• 580 
4.66 
. 617 
4 - 93 
f 2.0 
.205 
.90 
.274 
1.25 
• 33 i 
i -55 
.425 
2.05 
• 492 
2-39 
1 ... 
J 1.5 
• 257 
1. 20 
■335 
1.71 
.400 
2.17 
.500 
2.82 
•569 
3-30 
| 1.0 
•344 
1. 84 
•434 
2.60 
.501 
3-17 
. 607 
4.06 
.671 
4. 60 
l *5 
•529 
4.00 
.622 
4.92 
.690 
S-6i 
,770 
6.41 
.826 
6.98 
2.0 
• 300 
1.11 
•399 
1.81 
% 
2.42 
.625 
3-40 
•725 
4.09 
X . 
i -5 
•377 
i* Si 
•492 
2-55 
•589 
3-44 
•737 
4 - 79 
.847 
5. 80 
1.0 
•505 
2-39 
.636 
3-93 
•750 
5-30 
.908 
7.18 
1.013 
8-39 
•5 
. 782 
6.03 
•932 
8-02 
1.037 
9*43 
i -173 
11. 28 
1-263 
12.48 
HEAD, 1 FOOT 
2. O 
0. 250 
1.19 
0. 322 
1. 22 
0.386 
1.24 
0.488 
1.28 
0.561 
1-30 
2. 
1*5 
•3i4 
1.52 
•397 
x. 70 
• 467 
x.84 
•575 
2.08 
.648 
2- 22 
1.0 
.422 
2.40 
•514 
2. 80 
•590 
3-15 
.698 
3- 62 
.769 
3-92 
•5 
•655 
6.16 
• 74<5 
6.41 
.813 
6.61 
.896 
6.88 
•951 
7. 01 
2.0 
.300 
i*34 
•388 
1.49 
•465 
1.61 
•590 
1.82 
.680 
1.98 
xX . 
i- 5 
•378 
1. 78 
•477 
2. IO 
.562 
2.40 
•693 
2.85 
•78s 
3-17 
1. 0 
.508 
2.89 
.622 
3-53 
.714 
4.06 
•844 
4- 79 
•937 
5-31 
•5 
•795 
7.29 
.906 
7- 79 
.989 
8.18 
I.094 
8.64 
1-163 
8-95 
f 2.0 
•374 
1.60 
•489 
2.06 
.586 
2.44 
•758 
3*13 
00 
■S' 
3-55 
1 . 
J 1.5 
•47i 
2. 20 
.601 
2.92 
. 710 
3-55 
.888 
4-52 
1.003 
5-19 
1 1.0 
•643 
3-76 
• 787 
4.83 
.908 
5- 73 
1.083 
7. 07 
I. 200 
7.92 
l -5 
1.010 
9.20 
1.159 
10. 28 
1.271 
11.08 
1.410 
12.09 
1-503 
12. 72 
f 2.5 
.64 
3-3 
.818 
4.8 
.968 
6.07 
1.21 
8.07 
1*391 
9* 56 
2.0 
• 508 
2.30 
. 660 
3*64 
•799 
4.87 
1-013 
6. 73 
I. 202 
8.39 
x . 
1 1,5 
.640 
3-30 
.818 
4.80 
.969 
6.09 
1. 210 
8.08 
I-39I 
9-56 
I. O 
l -5 
.864 
1.390 
5-40 
11. 89 
I.077 
1.605 
7.58 
14.63 
1.258 
1. 782 
9-43 
16. 85 
1-505 
2.015 
n-95 
19.80 
1.688 
13.81 
Figure 16 shows the variation of the percentages of increase in the 
discharges through a i-foot rectangular notch, with heads of 0.6 foot and 
1 foot as the ratio of the cross-sectional area of the weir box (A) to the 
area of the weir notch (a), decreased with the use of different end 
and bottom contractions. From these curves it will be seen that chang¬ 
ing the position of the sides of the weir box and leaving the bottom in a 
fixed position has a greater effect upon the discharges than leaving the 
sides fixed and moving the bottom. This indicates that end contractions 
have more effect upon the discharges than do bottom contractions. 
With end contractions equal to 2 H and a bottom contraction equal to 
3 H, or end contractions equal to 3 H and a bottom contraction equal to 
2 H, the mean velocities of approach are about one-third foot per second 
and the discharges with medium to high heads do not agree closer than 
approximately 1 per cent with the discharges computed by the formula. 
