EXAMPLE PROBLEM II-6-3

FIND:

The width of the ebb jet and its maximum velocity along the centerline 2,000 m seaward from shore.

GIVEN:

The inlet channel width where the ebb jet exits the inlet is 200 m and the channel depth is 8 m. A flat

bottom and Mannings *n *= 0.02 are assumed. The maximum average velocity in the channel is 1.5 m/sec.

SOLUTION:

The friction factor (from zsy and nlata (1982)) is calculated as

(9.8) (100) (0.02) 2

'

' 0.08

'

0.75

(8) 0.75

where bo = half-width of channel = 200 m / 2 = 100 m and the dimensionless distance offshore parameter is

ξ'

with x, the distance offshore, equal to 2000 m. Calculating these parameters, = 0.08 and ξ = 20. Using

Figures II-6-32 and II-6-33, and interpolating for , the results are

Y

ξ ' 18.5

and

Y

(ξ) ' 0.2

Therefore, for a flat bottom, the half-width of the jet expands from 200 m to 1,850 m and the center-line

velocity of the jet decreases from 1.5 m/s at the inlet to 0.3 m/s 2,000 m from shore.

Hydrodynamics of Tidal Inlets

II-6-41

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