Page 400 - Civil Engineering Formulas

HYDRAULICS AND WATERWORKS FORMULAS 327

g 4 5/2
or Q zH m 5/2 (12.107)
B2 5

With g 32.16,
5/2
Q 2.295zH m (12.108)

Parabolic Channels
These channels can be conveniently defined in terms of the top width T and the
2
c
depth D . Then the area a 3 D T and the mean depth D .
m
c
Then (Fig. 12.21),
2
V c 3 gD c (12.109)
2
and D c 3 V c (12.110)
2 g
8g
Further, Q TD c 3/2 (12.111)
B27
With g 32.16,
3/2
Q 3.087TD c (12.112)
3 3 Q 2
and D c (12.113)
2 BgT 2

8g 3 3/2
3/2
Also, Q TH m (12.114)
B27 4
With g 32.16,
3/2
Q 2.005TH m (12.115)
T

D c

FIGURE 12.21 Parabolic open channel.