Full Equations Utilities (FEQUTL) Model for the Approximation
of Hydraulic Characteristics of Open Channels and Control
Structures During Unsteady Flow
The standard header block must always appear first in the input to FEQUTL. It defines the command names used in FEQUTL to process the subsequent input. Some values and options that control command processing in FEQUTL also are defined. The command names are changed infrequently, usually only when a new version of the software is released. Therefore, the common practice is to copy the standard header block from an available input file.
The number to the right of each command name in the standard header block is an internal control number for FEQUTL. The number must not be changed. The number is used to access the part of FEQUTL that completes the operations defined by the command. Changing the name of the command is inconsequential, but changing the internal control number changes the command drastically.
UNITS= ENGLISH (or METRIC )Selects measurement units. NCMD= 24 Number of commands present in standard header block FEQX 1 FLOODWAY 2 BRIDGE 3 CULVERT 4 FINISH 5 FEQXLST 8 SEWER 10 MULPIPES 11 FTABIN 12 EMBANKQ 13 CRITQ 15 GRITTER 16 MULCON 18 CHANRAT 19 EXPCON 20 HEC2X 21 QCLIMIT 22 XSINTERP 23 FEQXEXT 25 CHANNEL 26 WSPROX 27 WSPROQZ 28 WSPROT14 29 UFGATE 30 DZLIM= 1.0 Minimum water-surface height increment in output table; must be >0 NRZERO= 0.08 Minimum nonzero water-surface height in the table; must be > 0 USGSBETA=NO Selection of computation of and EPSARG=4.E5 Convergence criterion for CULVERT, EXPCON EPSF=1.E4 Convergence criterion for CULVERT, EXPCON EXTEND=NO Cross-section extension option.Explanation:
DZLIM and NRZERO are used to control the spacing of the
water-surface heights argument values in cross-section tables.
The list of water-surface heights in a cross-section table is
first developed from the unique water-surface heights values
defined by the breakpoints along the boundary of the cross
section. This list is then checked for an argument near zero.
If no argument near zero is available, the value given by
NRZERO is inserted as an argument. The list of arguments also
is checked to ensure that the interval between successive
arguments in the table is never greater than DZLIM. Both of
these parameters are provided to help control the errors of
interpolation in conveyance for the cross section. The
near-zero point is needed because the conveyance varies rapidly
near zero water-surface height, and linear interpolation in the
square root of conveyance at small water-surface heights is inaccurate if a near-zero argument is not in
USGSBETA defines the method utilized in computing the momentum
correction coefficient, , and the energy-flux
correction coefficient, , in a cross section. If
USGSBETA=NO, then = 1.0 and
= 1.0 in each subsection of the cross
section. If USGSBETA=YES, then the value of and in each subsection are computed with the
USGS method given in section 3.1.1.
EXTEND defines the procedure for extending or adjusting the channel boundary if the first and last point of a cross-section description are either not at the same elevation or are not the maximum elevation in the section. If EXTEND = YES, then a frictionless vertical extension of the channel boundary at either the first or last point, or both, is applied to match the maximum elevation found at any point in the cross section. The size of the extension is given in a warning message. If EXTEND=NO, then no extension is applied and the table is computed to the minimum of the elevations of the first and last point given on the boundary.
If one side of the cross section is extended in FEQUTL and then a water-surface elevation above the low side of the cross section is computed in FEQ, a warning message cannot be issued in FEQ simulation because only the cross-section table and not the cross section is considered in the FEQ computations. If the extension is large, the results from FEQ may be in error because a large part of the cross section is unknown. It is best to use EXTEND=NO and to manually adjust cross sections that have an inadequate vertical extent as determined in subsequent computations in FEQUTL or FEQ.
Examples of most commands and options for FEQUTL appear in the example input file FEQUTL.EXM. This file may be obtained by electronic retrieval from the World Wide Web (WWW) at http://water.usgs.gov/software/feq.html and by anonymous File Transfer Protocol (FTP) from water.usgs.gov in the pub/software/surface_water/feq directory.