LONGSHOfiE CURRENT (m/s) 



RMS WAVE HEIGHT (m) 



■ (e) Additional comparisons of model and observed current 

 profiles (a) and wave heights (b) suggest that more 

 energy is extracted from the wave field inshore of 

 the breaker zone than the model predicts. 



Figure 82. Comparisons of field observations of nearshore currents and 

 numerical model of Birkemeier and Dalrjmiple (1976) (from 

 Allender, et al., 1978). — Continued 



plus the lack of lateral mixing stress term. Allender, et al . (1978) cited 

 the surf zone model by Battjes and Janssen (1978) to handle bar and trough 

 bathymetry and the addition of lateral mixing stress terms as needed improve- 

 ments. 



The latest version (Ebersole and Dalrymple, 1979) includes the convec- 

 tive acceleration and lateral mixing terms but retains the wave breaking 

 ratio Y to specify the surf zone energy dissipation. Published comparisons 

 of numerical versus experimental results are unknown. As previously dis- 

 cussed (see Fig. 35), the present version contains sufficient numerical 

 viscosity to negate the quantitative reliability of the results for some 

 cases. All the above were finite-difference numerical models. 



An example of a finite-element solution for thd circulation eddy in 

 the lee of a harbor and some physical model data was previously presented 

 in Figure 36. No quantitative numbers were given to make a comparison. 

 This is also true for the finite-element model by Liu and Lennon (1978). 



Finally, it should be noted here that the complete experimental results 

 of Gourlay (1978) from his laboratory experiments with an offshore break- 

 water (Fig. 8) are included in his Appendix 4. Sufficient current, wave 

 height, and MWL information is presented to serve as a check on any of the 

 numerical models cited. Whereas confined laboratory basins posed problems 



209 



