48. A time-step of 18.0 sec and a drag coefficient c of 0.01 were used 

 in the simulation. Figure 18 shows the bathymetry at Oregon Inlet. A steady- 

 state condition was reached after a time of 67 At . Figure 19 shows the mean 

 water levels (setup and setdown) and Figure 20 the velocities calculated by 

 the model. The velocity vectors of Figure 18 are plotted just for every other 

 cell in each coordinate direction to reduce the number of vectors and thus 

 make velocity patterns more apparent. In addition, the plotting of velocities 

 with magnitudes less than 0.1 ft/sec is suppressed. 



49. Away from the inlet shown in Figures 18 and 19, the shoreline and 

 the contours are approximately straight and parallel. Thus, there is a small 

 setdown in the offshore area that is followed by a large setup. This is the 

 expected setup and setdown pattern for a plane beach. The velocities shown in 

 Figure 20 are mainly alongshore, and the velocity distribution is similar to 

 that for a plane beach. 



50. The setup, setdown, and velocity patterns are more complicated in 

 the region of the inlet (the central part of the grid). Here the breaker line 

 is farther offshore. The depth in the main channel decreases first and 

 increases later in the direction of the inlet. Because of these factors, the 

 water sets up around the inlet and tends to create a flow into the inlet 

 through the various channels. A part of the main alongshore flow goes around 

 the channels and s.hoals and thus bypasses the inlet. 



51. Near the shoals, the patterns of mean water level and velocity are 

 irregular. This is because the waves refract around the shoals and break, 

 creating local setups and currents that do not necessarily conform to the 

 general pattern. As the waves go toward the barrier islands, they sometimes 

 re-form after breaking because the depth increases. 



52. The central processor unit (CPU) time for running the Oregon Inlet 

 grid to a steady-state condition was approximately 15.5 sec on a CRAY-1 

 computer. The total cost for the job, including program compilation, CPU 

 time, and data file manipulation, was approximately $10. Thus the wave- 

 induced current and setup model is sufficiently efficient that it can be 

 applied to large practical coastal and inlet problems. If instead of an 

 alternating-direction implicit finite difference model that uses a variable 

 grid (the model described in this report) an explicit finite difference model 

 that uses a uniform grid were used in computations for Oregon Inlet, the 

 computational requirements would have been approximately 3,000 times greater. 



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