From XMS Wiki
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.
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.
- For more information on this solver, see page 84 of the USGS documentation.
GMS – Groundwater Modeling System
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