by Kirby (1983) are shown also in the figures (as a dashed line). Kirby 

 showed that much of the discrepancy between simulated and observed data could 

 be eliminated if a nonlinear wave theory were incorporated into the model. He 

 incorporated Stokes' second order theory (which he showed was valid for this 

 experiment) into his model, and the results also showed that nonlinear effects 

 became increasingly important after the waves pass profile 3. 



48. An interesting aspect of the RCPWAVE results is evident in pro- 

 files 3, 4, and 5. The lobed features in the wave height variation are 

 smoothed by the model. The cause of this smoothing is not known. It may be 

 caused by the dissipative interface or the point-to-point filter used in the 

 numerical scheme. The side lobes seem to be related to the occurrence of an 

 amphidromic point where the wave phase becomes multivalued and the wave height 

 variation contains a discontinuity. The solution scheme forces the magnitude 

 of the phase function gradient to be single valued. This may also cause the 

 local smoothing. The model is intended for use in open coast, prototype ap- 

 plications. For these types of problems, this smoothing property of the model 

 can certainly be tolerated. 



CERC's FRF Cases: Comparisons with Prototype Data 



49. In addition to the laboratory verification, RCPWAVE also was veri- 

 fied using field data collected at CERC's FRF in Duck, North Carolina. Bot- 

 tom bathymetric contours in the area are generally straight and parallel to 

 the coastline except in the immediate vicinity of the research pier. The 

 pier's presence has caused the formation of a deep scour hole along much of 

 its length. The complicated bathymetry, which has resulted from this hole, 

 was one reason for selecting the FRF for field verification. Hubertz (1981) 

 showed that a ray model using refraction theory alone proved incapable of sim- 

 ulating observed conditions. Hubertz (1982) also showed that a short wave 

 model which includes diffractive effects in its governing equations (the Sys- 

 tem 21 Mark 8 proprietary model developed by the Danish Hydraulic Institute) 

 could accurately simulate wave propagation in the vicinity of the pier up to 

 the breaking point. 



50. Another reason for selecting the FRF was the availability of 

 wave data, both offshore and along the pier. During October 1982, an exten- 

 sive, 1 -month field data collection program was undertaken. Two storms 



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