diffraction around the jetties. For this, the actual layout of the jetties is 

 used. The procedure was somewhat similar to that of Perlin and Dean (1983). 

 During the development of the subroutine and the procedure, several tests were 

 performed including comparison of its results to the laboratory data of Hales 

 (1980) for a single structure case, and to two physical hydraulic model tests 

 conducted at CEWES for the two jetty case. In each case, the results of the 

 subroutine compared favorably with laboratory data. In the grid for CURRENT, 

 the jetties were represented in a stair-step fashion similar to that in WIFM. 

 CURRENT treated them as thin-walled nonovertopping impermeable barriers. 



93. Because of the highly variable nature of the computational grid, 

 the wave model was run on a uniform grid with 500-ft by 500-ft cells, and its 

 results were interpolated to the variable grid. The wave and wave-induced 

 current models were run for each of the 79 wave conditions. There are no 

 waves or wave-induced currents corresponding to wave 80. Each of the wave 

 conditions represented the offshore boundary condition for the wave model. 

 The model was run for the condition, and its results were stored in the form 

 of wave height, direction, and wave number at each grid cell. They were next 

 used as input to CURRENT which computed and stored on a file the setup ri and 

 the two velocity components U and V for each grid cell for each wave. For 

 convenience the corresponding wave information for each cell was also stored 

 on the same file. Note that in general CURRENT used a time-step of 50 sec and 

 in each run calculations were continued until an approximate steady-state con- 

 dition was reached by the current field. 



Results 



94. For convenience, results for only three typical cases out of the 79 

 listed in Table 3 will be presented here. They have been selected so that 

 they represent waves coming from south and north of the shore-normal direction 

 and approximately along the shore-normal direction. It is convenient to pre- 

 sent the results from the wave and wave-induced current models in terms of the 

 uniform grid in the computational plane rather than the variable grid (Fig- 

 ure 3) . One advantage of this type of display is that the results for the 

 entire grid can be shown on an 8-1/2-in. by 11-in. sheet of paper. However, 

 there is a disadvantage in that cell centers are not at the proper distances 

 relative to each other. Thus, boundary cells appear much closer to the center 

 than they really are. Moreover, the cell dimensions are distorted. Cells 

 close to the inlet, the barrier islands, and the navigation channel appear to 



52 



