82. Nodes in a channel may be numbered starting from any number, 

 provided one of the channels begins with the number I and there are no missing 

 numbers. The largest node number will then equal the total number of nodes. 

 Nodes in a channel must be numbered consecutively starting at the beginning 

 node and ending in the end node of the channel. It is standard practice to 

 label the seaward node as node number I . 



83. System geometry is denoted by x- and y-coordinates . The x- 

 coordinate identifies positions across the channel cross section, and the y- 

 coordinate identifies distances in the longitudinal direction, that is, in the 

 direction of flow. Variable distances x and 7 provide a realistic representa- 

 tion of the system; for example, closely spaced nodal points are used where 

 significant changes take place in geometric properties. The value of y along 

 a channel increases from the beginning to the end node, and the starting value 

 of 7 is arbitrary. It is convenient for graphic display, but not necessary, 

 to measure distance from the sea boundary. 



General control parameters 



84. General control parameters are values controlling operation of 

 DYNLETl and consist of: 



a. Initial time. 



b. Termination time. 



c. Tolerance values for iteration convergence. 



d. Temporal weighting coefficient. 



e. Presence of wind. 



f. Computation time step. 



g. Number of iteration steps, 

 h. External boundaries. 



i. Internal boundaries. 



The general control parameters are given in the following. 



85. Initial time . An initial time TO, conveniently taken as the 

 chronological time of the modeled sequence in decimal hours, must be 

 specified. 



35 



