Water Resources Surface Water Software: Full Equations (FEQ) Model Web Resources
These notices are superseded by the release.txt distributed with the subsequent released versions of FEQ. User notices and bug reports (if any) for subsequent releases of FEQ and FEQUTL may also apply to this version.
NUMGT, the number of nodes at which the secondary relative convergence criterion may replace the primary relative convergence criteria, EPSSYS, should be set to zero for the final output. The use of NUMGT greater than zero was found to be a cause of an obviously invalid result in three models. The secondary relative convergence criterion is defined by a factor, EPSFAC, times EPSSYS. EPSFAC defaults to 2.0 unless the user assigns a value greater than 1.0. Values less than or equal to 1.0 are overwritten to 2.0. Therefore, do not input any value less than or equal to 1.0 for EPSFAC (or FAC in version 8.92).
The discussion of NUMGT in Franz and Melching (1997), p. 104, suggests that the use of the secondary relative convergence criteria has only small effects on the final results. Although there have been no other reported issues with the use of non-zero NUMGT since the 1997 report, caution is indicated. NUMGT can be helpful for obtaining diagnostic output in intermediate runs.
Posted: July 27, 2016
This affects only models using a side-weir instruction, code=14, where an optional time-series table is used to define a time-dependent factor on the discharge. Fac is erroneously applied as a constant value of 1 instead of referencing the time-series table. This bug was introduced in version 10.0, corrected in 10.72 (neither released here) and will be corrected in the next release or upon request.
The purpose of this factor is to simulate a side-weir failure of partial length.
Posted: November 13, 2015
Franz, D.D., and Melching, C.S., 1997, 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, 258 p.
U.S. Department of the Interior |
U.S. Geological Survey |
Illinois Water Science Center
URL: http://il.water.usgs.gov/proj/feq/bug_notice3.html
Page Contact Information: USGS FEQ support
Page Last Modified:
Thursday, July 28, 2016
