ERDC/CHL CHETN-IV-55
March 2003
Digital bathymetry covering Cook Inlet over a 49.9-km (31-mile) reach was used to carve the 3-D
model using a programmable router. Figure 6 shows a portion of the model carved into 7.8-cm
(3-in.-) thick Plexiglass. Relevant scaling factors (prototype-to-model ratios) for the 3-D model are
listed on Table 2 along with approximate model equivalences. The model had a horizontal-to-
vertical length scale distortion of 15.
Figure 6. Portion of 3-D Cook Inlet model looking downstream
Table 2
Scale Ratios for Three-Dimensional Cook Inlet Model
Scale
Scale Value
Model Equivalence
1,250 ft ≈ 1 in
Horizontal scale
NX = 15,000
Vertical scale
83 ft = 1 in
NZ = 1,000
1.6 m/s = 5 cm/s
Velocity scale
NV =
NZ = 31.6
Discharge scale
203,000 m3/s = 0.43 liter/s
NQ = NX NZ3/2 = 474,341,650
The model was divided into six sections over the 49.9-km (31-mile) reach, but only four sections
(about 32.2 km (20 miles)) could be placed on the flow table at a time. By removing sections on one
end and adding sections on the opposite end, different reaches of Cook Inlet could be tested with
adequate upstream boundaries represented in the model. This technique effectively extended the
modeled region with little additional cost.
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