ERDC/CHL CHETN-IV-32
June 2001
fL
= the bulk pipe friction factor for the cross-barrier pipe
D
L=
length of pipe through the barrier.
It is assumed that if the back face opening of the pipe is partially submerged, and the discharge
can be approximated as a free discharge. The classical pipe friction factor f is dependent on
DV
Reynolds number for the pipe, R =
where v = kinematic viscosity of water as well as the
ν
relative roughness of the pipe. The pipe friction factor ranges between 0.0001 to 0.1 and
diagrams with values are presented in any standard fluid mechanics text (e.g., Daugherty et al.
1985). It is also noted that the length of the pipe through the barrier typically equals the width of
the barrier unless the opening through the barrier is tortuous in which case it should be increased.
Configuration 4: Water Elevation on the Front Side of the Internal Barrier Greater
than Water Elevation on the Back Side; Water Elevation on the Front Side Greater
than the Crown Height of the Cross Barrier Pipe; and Water Elevation on the Back
Side Above the Crown Height of the Pipe
Water elevation on the front side of the internal barrier is greater than water elevation on the
back side; water elevation on the front side is greater than the crown height of the cross-barrier
pipe; and water elevation on the back side is above the crown height of the pipe (Figure 4). Thus
ζL >ζR
(8)
ζ L ≥ h p and
ζ R ≥ hp
(9)
Figure 4. Water elevation on the front side of the internal barrier greater than water elevation
on the back side; water elevation on the front side greater than the crown height of the
cross-barrier pipe; and water elevation on the back side above crown height of the pipe
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