GMS:DE4 Package

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MODFLOW
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Packages
Flow: BCF6, HUF, LPF, UPW
Solvers:

DE4, GMG, NWT, PCG,

PCGN, LMG, SIP, SOR,

SMS
Other:

BAS6, BFH, CHD1, CLN,

DRN1, DRT1, EVT1, ETS1,

GAGE, GHB1, GNC, HFB1,

HUF, LAK3, MNW1, MNW2,

OUT1, RCH1, RIV1, SFR2,

STR1, SUB1, SWI2, WEL1,

UZF1
v • e

The DE4 package or Direct Solver is one of the solvers available for MODFLOW. It requires reading in a DE4 file. The MODFLOW DE4 Solver package dialog will show the variables in the DE4 file. Variables include:

  • Comments (Text) – Allows up to 199 characters.
  • Maximum number of iterations (ITMX) – Per time step. Enter 1 for no interations.
  • Maximum number of upper equations (MXUP) – Impacts the amount of memory used by the package. Prints the actual number of equations in the upper part when the package runs.
  • Maximum number of lower equations (MXLOW) – Impacts the amount of memory used by the package. Prints the actual number of equations in the lower part when the package runs.
  • Maximum bandwidth (MXBW) – Impacts the amount of memory used by the package. Prints the actual band width plus 1 when the package runs.
  • Frequency of change of coefficients in [A] (IFREQ) – Affects the efficiency of solution. Can be 1,2, or 3.
  • 1 = The flow equations are linear and that coefficients of simulated head for all stress terms are constant for all stress periods.
  • 2 = The flow equations are linear, but coefficients of simulated head for some stress terms may change at the start of each stress period.
  • 3 = A nonlinear flow equation is being solved, which means that some terms in [A] depend on simulated head.
  • Print flag for convergence information per time step (MUTD4) – Can be 0, 1, or 2.
  • 0 = The number of iterations in the time step and the maximum head change each iteration are printed.
  • 1 = Only the number of iterations in the time step is printed.
  • 2 = No information is printed.
  • Head change multiplier (ACCL) – Normally this value is 1. A value greater than 1 may be useful for improving the rate of convergence when using external iteration to solve nonlinear problems.
  • Head change closure criterion (HCLOSE) – Not used if not iterating, but a value must always be specified.
  • Interval for time step printing (IPRD4) – Not used if not iterating, but a value must always be specified.

For more information on this solver see page 84 of the USGS documentation at http://pubs.er.usgs.gov/usgspubs/ofr/.

The MODFLOW DE4 Solver package dialog.

DE4 File Format

FOR EACH SIMULATION
 0.  [#Text]
 1.  ITMX   MXUP   MXLOW   MXBW
 2.  IFREQ  MUTD4  ACCL    HCLOSE   IPRD4

Item 0 is optional—“#” must be in column 1. Item 0 can be repeated multiple times.


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