Model of Huval and Wintergerst (1977) 



153. This is also a numerical lumped-parameter model inspired by 

 Keulegan's (1967) analytical model and is described in Appendix 4 of GITI 

 Report 6 (Huval and Wintergerst 1977). The basic concepts are similar to the 

 GLPM. In application to Masonboro Inlet, the inlet hydrodynamic system was 

 represented by five cross sections, starting with Cross Section 1 at the 

 seaward end of the jetty and ending at Cross Section 5 located approximately 

 500 ft inland of the inlet throat. The bay boundary condition was imposed at 

 Cross Section 5. A bay area of 1.9 x 10^ ft^ was derived from the tidal 

 prism. No attempt was made to simulate conditions along Masonboro Channel, 

 Banks Channel, and Shinn Creek. A Manning's friction coefficient of 0.027 was 

 used throughout as compared with a value of 0.037 in the application by 

 Seelig, Harris, and Herchenroder (1977). The model was calibrated with the 

 September 1969 data and applied to predict conditions in November 1964 (prior 

 to jetty construction) and July 1966 (modified inlet and jetty condition). 

 This model does not appear to have been verified with the 1974 data. The 

 maximum flood and ebb tides computed by the model were 57,000 and -53,000 cfs, 

 compared with estimated measured values of 42,000 and -42,000 cfs. The 

 reasons for the systematic overestimations are not known. 



Evaluation of Flow Parameters from DYNLETl 



154. DYNLETl is based on the complete hydrodynamic equations in one 

 dimension (along the direction of the main flow) , and the numerical implemen- 

 tation does not require modification or simplification of the governing 

 equations. Analytical models or simple numerical models developed in the past 

 depended on linearization or other simplifications to solve the equations. 

 Such modifications were necessary in the precomputer era. The most common 

 procedures adopted were elimination of the temporal acceleration term, 

 elimination or linearization of the convective acceleration term, and lineari- 

 zation of the bottom friction stress term. For example, the ALPM incorporates 

 simplifications of the governing equations, with the temporal acceleration 

 neglected, the convective acceleration and the pressure head computed in a 

 gross sense (between the ends of the inlet) , and the bottom friction stress 

 considered to be the predominant governing physical mechanism. 



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