7 3-D Cook Inlet Model
During 7-9 May 2002, engineers from the Alaska District participated in
experiments using the two idealized flow models. Results from the tests
appeared to reproduce the primary flow patterns in the vicinity of the Port of
Anchorage and identified the potential mechanism responsible for sediment
deposition in the harbor. Everyone involved in the experiments agreed that a
small-scale flow table model incorporating the actual 3-D bathymetry would
provide more reliable flow patterns and greater understanding of the shoaling
process. At the same time it was realized that extending the model coverage both
upstream and downstream from the Port of Anchorage would better enable
Alaska District engineers to assess potential remedies.
Additional funding was provided to construct and test a physical model of
Upper Cook Inlet featuring 3-D bathymetry. The objective of the 3-D model was
to identify and examine the large-scale flow patterns in upper Cook Inlet during
maximum ebb and flood tide. A secondary objective was to investigate impacts
related to various dredge release sites to optimize dredging operations.
3-D Cook Inlet Model Description
Model scaling and bathymetry
Figure 58 shows the portion of upper Cook Inlet that was scaled and
reproduced for testing in the CHL precision flow table. The bounded rectangle in
the figure measures approximately 18.2 by 51.2 km (11.3 by 31.8 miles) for a
total area of about 932 sq km (360 square miles). The shorter dimension was
scaled to fit within the 1.22-m (4-ft) width of the flow table. Using the same
horizontal scale, the longer dimension scaled to 3.4 m (11.17 ft), which exceeded
the 2.4-m (8-ft) length of the flow table, but gave the desired extended model
coverage.
The longer dimension of the model was divided into six equal-length sections
measuring 56.64 cm (22.3 in.) each. This provided the capability of testing any
four adjacent sections in the flow table. For example, during ebb flow, a greater
distance upstream from the Port of Anchorage could be placed on the flow table
to assure better replication of the upstream boundary conditions. When the
model was reversed in the flow table to simulate flood tide, the sections south
of Fire Island could be included. This methodology proved to be useful for
extending the region that could be examined using the flow table by adding and
removing sections.
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Chapter 7 Three-Dimensional Cook Inlet Model
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