C

=

overall flooding coefficient (dimensionless)

a

=

cross section area of main culvert (sq ft)

g

=

acceleration of gravity (fps/s)

h

=

difference in elevation between water in drydock

and outside water (ft)

To determine the relationship between a varying head, as the water rises

in the drydock, and an interval of elapsed time, take the expression in Equation 2:

EQUATION:

Q/A = -dh/dt, fps

(2)

where:

A

= average plan area of the water pond in a drydock

(sq ft)

Then substituting the value of Q from Equation 1:

= -A/Ca x dh/√(2gh)0.5

EQUATION:

dt

(3)

Or for definite time intervals (integrating Equation 3 between limits h2 and

h1 )

EQUATION:

t2 - t1 = 2A((√h1) - (√h2)) / Ca√ (2g) seconds

(4)

For total time T, where the original difference in water levels was H:

EQUATION: T = 2A √(H) / Ca √(2g) seconds

(5)

The value of C may be obtained from tests on drydocks or other structures

such as ship locks with comparable flooding systems. For proposed flooding systems

of unusual character, or for drydocks of unprecedented size, model tests should be

considered.

6-6

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