Page 529 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch13_457-499.qxd 8/7/10 8:49 PM Page 487

13.10 Street Inlets 487

From Eq. 13.34,
R f l K cf (V V 0 )
1 0.090 (3.45 3)
1 0.04 0.96
From Eq. 13.35,

K cs V 1.8 -1
R s = a1 + 2.3 b
S x L
0.15 * 3.45 1.8
R s = 1na1 + b
0.056 * 2 2.3
0.15 * 9.29
= 1na1 + 2.3 b
0.056 * 2
= 0.165
From Eq. 13.36,
Q i Q w R f Q s R s
0.92 0.96 (1 0.92) 0.165
3
3
0.8832 0.0132 0.8964 ft /s 0.90 ft /s (25 L/s)
3
The flow intercepted by the grate inlet 0.90 ft /s (25 L/s).
Solution 2 (SI System):
From Examples 13.14 and 13.15:
3
Q g = Q = 28.3 L/s = 0.0283 m /s
T = 0.985 m
W g = 0.61 m
L = 0.61 m (Given)
d = 55 mm = 0.055 m
S L = 2% = 0.02
S x = 5.6% = 0.056
3
Q w = 26 L/s = 0.026 m /s
A g = triangle area of gutter flow = Td>2 = 0.985 * 0.055>2 = 0.027 m 2
V = Q g >A g = 0.0283>0.027 = 1.05 m/s
Given V 0 = 0.91 m/s
From Eq. 13.34:
R f = 1 - K cf (V - V 0 )
R f = 1 - 0.295 (1.05 - 0.91) = 1 - 0.04 = 0.96
From Eq. 13.35:
K cs V 1.8 -1
R s = a1 + 2.3 b
S x L
0.0828 * 1.05 1.8 -1
R s = a1 + b = 0.165
0.056 * 0.61 2.3