EM 1110-2-1100 (Part III)
30 Apr 02
EXAMPLE PROBLEM III-2-2
FIND:
Calculate the potential immersed-weight and volumetric longshore sand transport rates.
GIVEN:
The same conditions as in Example Problem III-2-1, except assume a median grain size D50
corresponding to a K coefficient = 0.60. Assume κ = 1 for simplicity.
SOLUTION:
With Hb rms = 2.0 m (6.6 ft), ρ = 1,025 kg/m3 (1.99 slug/ft3), ρs = 2,650 kg/m3 (5.14 slug/ft3),
g = 9.8 m/sec2 (32.2 ft/sec2) and αb = 4.5E, Equation 2-6d gives
3
5
2
ρg
2
IR ' K
Hb rms
sin(2αb)
1
2
16 κ
3
5
2
(1025) (9.81)
sin(24.5o) 1050 N/sec (236 lbf/sec)
2
0.60
(2.0)
16 (1)
This potential immersed-weight transport rate may be converted to a potential volumetric rate by using
Equation 2-7b
5
ρ g
2
Hb rms sin(2αb)
QR ' K
1
2
16 κ (ρs & ρ) (1 & n)
1
5
2
(1025) (9.81)
(2.0) 2 sin(24.5o)
QR ' 0.60
16 (1) (2650 & 1025) (1 & 0.4)
QR = (0.109 m3/sec) (3600 sec/hr) (24 hr/day)
QR = 9.4 x 103 m3/day (12.3 x 103 yd3/day)
III-2-18
Longshore Sediment Transport
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