to large bay systems as compared, with two-dimensional models because the 

 primary flow directions are known and cross -sectional data at high resolution 

 can be represented in the main inlet. Inlets with multiple channels are also 

 appropriately modeled with DYNLETl. Transition head losses arising from 

 sudden changes in channel width are well modeled by the one -dimensional 

 approach taken here; rigorous description of this phenomenon in 

 two-dimensional models is unknown to the authors. 



10. The model DYNLETl also provides an alternative to the "linked-node" 

 models developed in the 1960's (Roesner, Aldrich, and Dickinson 1989). 

 Standard linked-node models use explicit numerical solution schemes and, 

 therefore, have restrictions severely limiting the size of the allowable time 

 step. Also, channel cross sections must be greatly idealized, use of local 

 bottom friction coefficients is not possible, and only an average velocity for 

 a cross section can be obtained (as opposed to computing local velocities at 

 different stations corresponding to different locations along a cross 

 section). These and other limitations inherent in the linked-node models, 

 which were originally developed for pipe flow analysis, do not exist in 

 DYNLETl . 



11. As will be described in subsequent chapters, DYNLETl can analyze 

 the flow in channels of varied geometry, ranging from prismatic channels to 

 natural channels with flood banks, and it accepts varying friction factors 

 across an inlet channel, geometric data at variable distances across and along 

 an inlet channel, and a variety of boundary conditions. Flooding and drying 

 on the channel banks are automatically part of the calculation process if the 

 cross sections include these areas. Values of water surface elevation and 

 average velocity are computed at locations across and along inlet channels, 

 and displayed on the computer monitor and written to output files for possible 

 further analysis and enhanced visual display. The inlet to be modeled may 

 consist of a single channel connecting the sea to the bay, or it can be a 

 system of interconnected channels, with or without bays. 



12. The numerical model also includes a number of useful enhancements 

 beyond simply implementing an efficient and accurate numerical solution 

 scheme, including incorporation of a transition- loss term, user- friendly 

 interface for data entry, preparation of data files for viewing on the 

 monitor, and printer output of cross -section geometry, velocity, and stage. 



7 



