1.6
Conventional Froude Limit
Oil Creek 1988
For Ice Cover Formation
(effective)
Allegheny River 1982-83
1.2
(effective)
Salmon River
1989-90 (ineffective)
1990-91 (effective)
0.8
Oil Creek1982-83
(ineffective)
Oil Creek 1981-82
(ineffective)
0.4
0
0.1
0.2
0.3
a. Sag boom.
Froude Number
Figure 6. Froude number vs. flow depth for prototype
booms.
Q
b. Shear boom.
23.5
265
'
42.5
266'
0'
28
34.7
c. Sag and shear ice booms during testing.
Figure 8. Model booms.
where the velocity was at a maximum. The anchor
positions allowed the boom to sag in the direction
of maximum velocity rather than taking advan-
Figure 7. Salmon River ice boom geometry.
tage of the lower velocities and shallower depth
on the left bank of the river (Fig. 7).
the critical velocity had been exceeded at the boom
In May 1990, researchers at CRREL tested the
and a reduction in surface velocity was needed.
shear boom concept in the laboratory in an effort
The current geometry of the boom carried incom-
to increase the frazil ice capture rate for the Sal-
ing frazil ice pans to the outside of a riverbend,
mon ice boom (Fig. 8). Model ice booms were built
6
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