﻿ Suggested input values for the NWT input file

# Online Guide to MODFLOW

 Navigation: Groundwater Flow Process > Solvers > NWT - Newton Solver Table 2. Suggested input values for the NWT input file

[Dashes (–) indicate that values are not applicable]

 Input variable name Default values Range Iteration Control HEADTOL 1×10-4 (L)* – FLUXTOL 500 (L3/T)* – MAXITEROUT 100 10–2,000 Dry Cell Tolerance THICKFACT 0.00001 1×10-6-1 NWT Options LINMETH 1 1 or 2 IPRNWT 0 0 or 2 IBOTAV 0** 0 or 1 Under relaxation Input Model Complexity Simple Moderate Complex DBDTHETA 0.97 0.90 0.85 0–1 DBDKAPPA 0.0001 0.00001 0.00001 0–1 DBDGAMMA 0.0 0.0 0.0 0–1 MOMFACT 0.0 0.1 0.1 0–1 Residual Control Model Complexity Simple Moderate Complex BACKFLAG 0*** 0 1 0 or 1 MAXBACKITER 20 20 50 1–100 BACKTOL 1.5 1.1 1.1 1–2 BACKREDUCE 0.97 0.9 0.7 0.05–0.99 Linear Solution Control and Options for GMRES Model Complexity Simple Moderate Complex MAXITINNER 50 50 50 25–1,000 ILUMETHOD 2 2 2 1 or 2 LEVFILL 1 1 1 5–10 for ILUMETHOD=1 0–2 for ILUMETHOD=2 STOPTOL 1×10-10 1×10-10 1×10-10 1×10-8-1×10-12 MSDR 5 10 15 5–20 Linear Solution Control and Options for χMD Model Complexity Simple Moderate Complex IACL 1 1 2 0,1, or 2 NORDER 0 0 0 0,1, or 2 LEVEL 1 1 15 1–10 NORTH 5 10 1 4-10 for Orthomin 2 otherwise IREDSYS 1 1 1 0 or 1 RRCTOLS 0.0 0.0 0.0 0–0.0001 IDROPTOL 1 1 1 0 or 1 EPSRN 5×10-3 5×10-3 1×10-3 5×10-5-1×10-3 HCLOSEXMD 1×10-3 1×10-3 1×10-4 1×10-3-1×10-5 MXITERXMD 50 100 200 25–1,000

*These values are dependent on the units specified in the MODFLOW-2005 discretization input file. Values given are for units of meters and days.

**The optimal value for IBOTAV is problem specific. Values of 0 and 1 should be tested for each problem.

***BACKFLAG should be set to 0 (residual control set to inactive) unless there are convergence problems. “OPTIONS” must be set to “SPECIFIED” if the residual control option is used.

Created with Help & Manual 8 and styled with Premium Pack Version 4 © by EC Software