the inlet throat (constriction) (Fig. 8a). Maximum currents are approximately 1.3 m/sec.
The longshore current is approximately 0.4 m/sec, and the current near the north jetty tip
is approximately 0.9 m/sec. With inclusion of waves from the WNW, the flood tidal
currents are reinforced on the north side of the inlet, and the longshore current increases
to 1.6 m/sec (Fig. 8b). Currents near the jetty tip increase significantly with the inclusion
of wave-induced currents (from 0.9 to 2.6 m/sec). In Fig. 8c, the confluence of flood tide
and WSW wave-induced currents are strengthened along the south side of the north jetty
(2.8 m/sec). Two bands of northward-directed flow are controlled by bathymetric features,
and a flow reversal (southward current) is observed for approximately 500 m north of the
north jetty. A clockwise gyre is also present in this region.
Fig. 9a shows ebb tidal currents are strong in the inlet throat and then diminish upon
exiting the flow constriction. Maximum currents are approximately 1.5 m/sec in the inlet
throat and the longshore current is approximately 0.2 m/sec. Fig. 9b shows that the
confluence of the ebb current and the north-to-south wave-induced current creates a
southbound current across the inlet throat. The ebb jet is deflected and re-directed to the
south. The longshore current is approximately 1.4-1.5 m/sec. Currents on the south side
of the north jetty are approximately 2 m/sec and oppose the ebb flow. Waves from the
WSW create a northward longshore current (1.3 m/sec) that intersects with the ebb jet to
create a large gyre in the inlet (Fig. 9c). Currents in the gyre approach 2 m/sec. Again, a
flow reversal (southward current) is observed for approximately 500 m north of the north
jetty. Currents on the south side of the north jetty are approximately 2.6 m/sec and oppose
the ebb flow.
CONCLUSIONS
Coupling of wave and circulation models for both an idealized inlet setting and an
application for Grays Harbor, Washington, concentrating on the influence of waves on
currents, has been presented. This coupling technology is necessary to represent strong
interactions between waves and currents in the surf zone and inlet. Comparison of tidal
current simulations to tidal-plus-wave-induced current simulations shows that the
interactions create gyres, longshore currents, rip currents, and "shadow zones" of relatively
weak currents.
Model coupling for an idealized inlet gives physical insights into such processes as
determining areas where interactions are most significant and inlet flood and ebb
dominance zones. Coupling also provides calculation insights for improving representation
of the phenomena, such as how to transition between non-coincident model boundaries,
cell resolution in strong wave-current interaction areas, and cell size compatibility between
finite difference and finite element models.
Model coupling for the Grays Harbor, Washington, numerical study illustrates
complexities of any real-world application such as additional bathymetric features,
structures, shoreline offset, and non-uniform grid resolution. The Steering Module
successfully demonstrated that coupling of wave and circulation models in this complex
environment is both attainable and necessary to capture the interactions that occur in
nature.
Cialone, Militello, Brown, and Kraus
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