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Full Equations (FEQ) Model for the Solution of the Full, Dynamic Equations of Motion for One-Dimensional Unsteady Flow in Open Channels and Through Control Structures

U.S. GEOLOGICAL SURVEY WATER-RESOURCES INVESTIGATIONS REPORT 96-4240

13.14 Free-Node Initial Conditions Block--Free-Node Table


Purpose: The sign, elevation, and initial values of any free nodes are assigned with this block. This block is required only if the system has free nodes. Free nodes are present whenever twice the number of branches is less than the number of flow-path end nodes. The maximum number of free nodes allowed in FEQ is specified in the parameter MNFREE in the INCLUDE file ARSIZE.PRM (appendix 3). This number may be increased as necessary and FEQ recompiled.

Heading: One line of user-selected information. The suggested string is FREE NODE INITIAL CONDITIONS.

LINE 1

Variable: HEAD

Format: A80

Example: NODE DEPTH DISCHARGE DEP DATUM SIGN

Explanation: This is a user-selected heading for subsequent information.

LINE 2 (one for each free node)

If NODEID=NO then

Variables: NODE, DEPTH, DISCH, ELV, SIGN

Format: I5, 3F10.0, I5

If NODEID=YES then

Variables: NODE, NAME, DEPTH, DISCH, ELV, SIGN

Format: I5, 1X, A8, 1X, 3F10.0, I5

Explanation:

NODE is the node label of the free node.

NAME is an optional name for the free node.

DEPTH is the initial water-surface height at the free node.

DISCH is the initial discharge at the free node.

ELV is the elevation of the reference point defining the datum for water-surface height at the free node. If this datum is zero, then water-surface height and water-surface elevation are the same. Assigning a zero value is often a good choice for level-pool reservoirs and generally is the most convenient choice for other free nodes.

SIGN is the sign of the free node (+1 or -1 ). The sign for each of the free nodes is read in FEQ simulation to be consistent with input data from older versions of FEQ. In Version 7.0 and later, however, the sign of each free node is determined from the Network-Matrix Control Input. A warning message is issued for incorrect signs, and the correct sign from context in the Network-Matrix Control Input is applied. A downstream and an upstream node should have positive and negative signs, respectively.

No terminator is needed for this block because the number of free nodes is known at this point in the analysis of the input.


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