142. Total time required to set up DYNLETl for modeling Masonboro Inlet 

 was approximately 40 person hours. Cross -section elevation data were read 

 from available plots and maps (12 to 37 points per cross section) , as were 

 other data such as the time -dependent water elevation boundary condition. 

 Approximately 1 day was required to run the model several times, graph and 

 output results, and conclude that the model was accurately calculating tidal 

 flow velocity, stage, and discharge. 



143. A 16 -hr run with an 1,800 -sec (30 min) time step for Masonboro 

 Inlet, consisting of five channels, two junctions, and 25 nodes took 57 sec 

 (Pascal -language version of the model) and 50 sec (C- language version) on a 

 386-based 25-MHz processor with a math coprocessor. On a 486-based 25-MHz 

 processor, the run times were less than half the preceding values. 

 DYNLETl calculation results 



144. Using the cross -sections obtained from hydrographic survey maps 

 and the tidal elevation and velocity measurements for the interval 09:00 to 

 18:00 Eastern Standard Time, 12 September 1969, with the boundary conditions 

 specified in the input file, the flow at Masonboro Inlet was modeled using 

 DYNLETl. (All input and output data for the Masonboro Inlet example are given 

 in Appendix A. ) 



145. The model can produce output in several formats. For comparison 

 with measured values, average velocities were computed at several points in 

 the cross-sections at Nodes 6, 13, 19, and 25, corresponding to velocity 

 gaging stations in the inlet throat, Masonboro Channel, Shinn Creek, and Banks 

 Channel, respectively. Comparisons of the computed and measured velocities at 

 the inlet throat (Node 6) are given in Figures 8 and 9 for Gages 2C and 2S 

 respectively, and additional velocity plots are given in Appendix A. Computed 

 velocities are shown as solid lines, and measured velocities are shown as 

 dashed lines. Because the exact correspondence between the data points in the 

 cross section and the location of the gaging station is not known, it is 

 expected that one or more of the model calculation points shown would repre- 

 sent the gaging station. Considering the uncertainties in modeling this 

 complex natural environment, DYNLETl performed well in reproducing magnitudes, 

 ranges, and phases of the velocities with use of only the two original esti- 

 mates of the bottom friction coefficient. It should also be noted that 

 accurate and comprehensive field measurements are very difficult to obtain, 



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