90
Coastal Engineering: Theory and Practice
where,
Hsb - wave height at breaking point, Cgb = wave group celerity at breaking point,
ab = wave direction at breaking point, Cgb — Lb/T\Lb calculated in
part a)
= 44.32/9 = 4.92 m/s
sin2ab = sin(2 x (-15.59)) = -0.517728399
The breaker wave height is given by
_
„
.
1
2fcd \
Cgb = n x Cb, where, n = - 1 + . .
,
2 \
smh 2/vd /
K = 2tt/Zzô, K = 27T/44.3198 = 0.1417,
Hb = 0.78db, db = Hb/0.78, db = 1.9925/0.78 = 2.5545 m
1 /
2 x 0.1418 x 2.554 \
n = - 1 +
---------------------- - ] = 0.9588
2 \
smh(2 x 0.1418 x 2.554) /
Cb = Lb/T = 44.32/9 = 4.92 m/s,
Cgb = n x Cb = 0.9588 x 4.92 = 4.7216 m/s
By Snell’s Law,
sin qq _ Cq
sin ab
Cb '
ab = sin'
14.04
4.92
x -0.7660
-15.59°
P, -
o
1024 x 9.81
is
. „ -n.sb(~ygb sin 2o(, —
—-----w
16
= -6355.36 N/s
x 1.99252 x 4.92 x -0.5177
Q (1290/12) x ( 6355.36) = —683201 m3/month
Similarly for other months the calculations are tabulated below.