Anchorage. The small-area idealized model also provided valuable insight into
the tidal flow regime near the port. Observations made in these two idealized
models were the stimulus for constructing a flow table model incorporating 3-D
bathymetry.
Task 3: Turbulence scale effect in distorted physical models
A theoretical analysis and an extensive set of experiments were performed to
assess potential turbulence scale effects that might arise due to flow separation
and associated turbulence in geometrically distorted physical models. Results
from these experiments will assist in determining whether a large-scale distorted
physical model of Cook Inlet will produce reliable and useful results in regions
where flow separation and turbulence are contributing to sedimentation.
Four distinct cases were examined: (a) Flow separation at a vertical edge
resulting in a free jet, (b) Flow separation at a vertical edge with a constrained
jet, (c) Flow separation at sloping edge resulting in a free jet, and (d) Flow
separation at a vertical step. In all cases differences due to model distortion were
evaluated by comparing the measured velocity fields of the prototype experiment
with the velocity fields of the distorted models scaled to prototype size using
appropriate scale ratios.
Task 4: Effect of sloping transitions on flow hydrodynamics
The objective of this task was to test the hypothesis that sloping transitions
on both ends of the harbor would decrease areas of reduced flow and increase
flushing of the harbor. Tests were conducted using vertical and sloping
transitions between deeper dredged areas and the shallower adjacent channel
profile. Both transitions were tested for the cases of flow leaving the harbor area
and flow entering the harbor. The relative effect of the transitions on the flow
was quantified with velocity measurements, and dye injections provided visual
qualitative assessment.
Task 5: Large-area 3-D flow model of Cook Inlet
The objective of this task was to identify and examine in a 3-D flow table
model the large-scale flow patterns in upper Cook Inlet during maximum ebb and
flood tide. The 3-D model of Cook Inlet featured actual bathymetry reproduced
at very small scale and with significant geometric distortion. Nevertheless, the
large-scale flow features such as flow separation at major headlands and gyre
formations resembled known flow behavior observed at the study site by Alaska
District engineers. The capability of extending the study area in both directions
by adding and removing sections enabled more replication of the critical
upstream boundary conditions, thus assuring better simulation of flow conditions
in the region of interest. The 3-D model was also used to examine potential sites
for dredged sediment disposal that minimized risk of sediment moving back into
the harbor.
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Chapter 8 Summary and Conclusions
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