Full Equations Utilities (FEQUTL) Model for the Approximation
of Hydraulic Characteristics of Open Channels and Control
Structures During Unsteady Flow
Notes: The rule for interpolation is identical to that used in branches in FEQ (linear interpolation at constant depth). The resulting cross-section tables contain all the distinct breakpoints in the pair of available tables used to define them. The maximum arguments for the intermediate tables are set to the smaller of the maxima for the defining pair of tables. Interpolation over large distances may not be valid, so this command must be used with caution.
LINE 1
Variable: SFAC
Format: 5X, F10.0
Example: SFAC = 5280.0
Explanation:
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SFAC is the multiplying factor for converting the stations for the nodes given in the single Branch Description Block (section 13.2) in the FEQ input (Franz and Melching, 1997) used to specify the interpolation. In this example, the stations given in the Branch Description Block are in miles. |
LINE 2
Variable: NODEID
Format: 7X, A4
Example: NODEID = YES
Explanation:
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NODEID indicates whether an identification string is used for the nodes on a branch. NODEID = YES indicates that an identification string of up to eight characters may be given in the branch tables for each node on a branch. The string may be left blank if no printed node identification is desired. However, space for the string is still required when it is blank. |
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HEAD is a user-defined heading to describe the information on subsequent lines. This information is the same as for a Branch Description Table (section 13.2) in the FEQ input (Franz and Melching, 1997), but with options suppressed. |
If NODEID = NO, then
If NODEID = YES, then
Explanation: The values describing each node on the single pseudo branch used in XSINTERP to define the interpolation are specified on this line.
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NODE is the node number. The end of the branch table is
indicated by assigning a negative value for the NODE entry.
The remainder of the line containing the terminating node
number may be blank. The number for the first node on each
branch must be given. The NODE column may be left blank for
the other nodes, and the node number will be computed in FEQ
simulation.
NAME is the optional identification string for the node. XTAB is the number of the table giving the hydraulic characteristics of the cross section at the node. X is the station of the node. Z is the elevation of the minimum point in the stream at the node. |
Interpolation is requested with the XTAB input described as follows. The station and elevation given on this line are used in FEQUTL unless the table option for these fields is invoked. If the elevation and station for the node are to be determined from the given cross-section table, the string 'TAB' or 'tab' must be inserted in either the elevation or the station column. The cross-section table must have already been input with FTABIN (section 5.13) or must have been stored with the SAVE option (sections 5.8,5.9,5.10). Not all the values need to be given for each node.
To request interpolation of a cross-section table, a negative cross-section table number at the node at the location requiring a table must be assigned. A positive table number must be present at some point above and at some point below the point of interpolation. More than one table can be interpolated between available tables. A minus sign in the rightmost column of the field for the table number indicates that an available table number will be used for interpolation in FEQ simulation. The user must ensure that any table number used in FEQUTL does not conflict with any other used in either FEQUTL computations or in FEQ simulation. The next unused table numbers are always taken in FEQUTL computations and FEQ simulation. A table number may be selected in FEQUTL computations or FEQ simulation that will appear in a subsequent command. If the station and elevation values are given, they will be used. The interpolation of hydraulic characteristics is done for given water-surface heights as a weighted average of the values at the measured cross sections surrounding the given location (station) with the weights linearly proportional to the distance from the given location to the measured cross section. Because the interpolation is done for hydraulic characteristics at given water-surface heights, the specified value of the thalweg elevation is only used to determine the bed slope of the stream in the vicinity of the interpolated cross section. If the station and elevation values are omitted, the station values are distributed uniformly and interpolated linearly for the elevation in FEQ simulation.