Quoted from: https://www.usgs.gov/software/conduit-flow-process-cfp-a-program-simulate-turbulent-or-laminar-groundwater-flow 

The conduit flow process for MODFLOW-2005 (CFP) has the ability to simulate turbulent or laminar groundwater flow conditions by:

1. coupling the traditional groundwater flow equation with formulations for a 1-dimensional discrete network of cylindrical pipes (Mode 1, CFPM1),
2. inserting a high-conductivity flow layer that can switch between laminar and turbulent flow (Mode 2, CFPM2), or
3. simultaneously coupling a discrete pipe network while inserting a high-conductivity flow layer that can switch between laminar and turbulent flow (Mode 3, CFPM3).

Conduit flow pipes (CFPM1) may represent:

• large dissolution features, such as submerged caves in carbonate aquifers or large voids from dissolution of burrowed carbonate rock;
• voids in fractured rock;
• lava tubes in basaltic aquifers; and
• submerged abandoned mines.

Pipes can be fully or partially saturated under laminar or turbulent flow conditions, but should be generally horizontal and full if vertical.

Preferential flow layers (CFPM2) may represent:

• a porous media where turbulent flow is suspected to occur under the observed hydraulic gradients;
• a single secondary porosity subsurface feature, such as a well-defined laterally extensive underground cave;
• or a horizontal preferential flow layer consisting of many interconnected voids.

In this second case, the input data are effective parameters, such as a very high hydraulic conductivity, representing multiple features.

The Conduit Flow Process for MODFLOW-2005 was developed with the support of the USGS Groundwater Resources Program.

Download Current Version of CFP

The current release is CFP v.1.8, released February 23, 2011.  The zip file includes a release history, installation instructions, source code, examples, and documentation.

• CFP version 1.8

Documentation for CFP

Shoemaker, W.B., Kuniansky, E.L., Birk, S., Bauer, S., and Swain, E.D., 2007, Documentation of a Conduit Flow Process (CFP) for MODFLOW-2005: U.S. Geological Survey Techniques and Methods, Book 6, Chapter A24, 50 p.

Published Reports and Articles for CFP

Kuniansky, E.L., 2014, Taking the mystery out of mathematical model applications to karst aquifers -- A Primer, in E. L. Kuniansky and L.E. Spangler, editors, U.S. Geological Survey Karst Interest Group Proceedings, Carlsbad, New Mexico, April 29 - May 2, 2014, pp. 69-81. http://dx.doi.org/10.3133/sir20145035.

Gallegos, J.J., Hu, B.X., and Davis, Hal, 2013, Simulating flow in karst aquifers at laboratory and sub-regional scales using MODFLOW-CFP: Hydrogeology Journal, v. 21, p. 1749-1760.

Saller, S.P., Ronayne, M.J. and Long, A.J., 2013, Comparison of a karst groundwater model with and without discrete conduit flow: Hydrogeology Journal, v. 21, no. , p. 1555-1566.

Kuniansky, E.L., Gallegos, J.J., and Davis, J.H., 2011, Comparison of Three Model Approaches for Spring Simulation, Woodville Karst Plain, Florida, in Kuniansky, E.L., ed., U.S. Geological Survey Karst Interest Group Proceedings, Fayetteville, Arkansas, April 26-29, 2011: U.S. Geological Survey Scientific Investigations Report 2011-5031, p. 169-170.

Reimann, T., Rehrl, C., Shoemaker, W.B., Geyer, T. and Birk, S., 2011, The significance of turbulent flow representation in single-continuum models, Water Resour. Res., 47, W09503, doi:10.1029/2010WR010133.

Reimann, T., Geyer, T., Shoemaker, W.B., Liedl, R. and Sauter, M., 2011, Effects of dynamically variable saturation and matrix-conduit coupling of flow in karst aquifers, Water Resources Research, v. 47, W11503, doi:10.1029/2011WR010446.

Reimann T. , Birk, S., Rehr, C., and Shoemaker, W. B., 2011, Modifications to the Conduit Flow Process Mode 2 for MODFLOW-2005: Ground Water, doi: 10.1111/j.1745-6584.2011.00805.x

Hill, M. E., Stewart, M. T. and Martin, A., 2010, Evaluation of the MODFLOW-2005 Conduit Flow Process: Ground Water, 48: 549–559. doi: 10.1111/j.1745-6584.2009.00673.x

Ashok K.C. and Sophocleous, M.A., 2009, Recent MODFLOW developments for groundwater modeling: Kansas Geological Survey Open-file Report 2009-4, 139 p. http://www.kgs.ku.edu/Hydro/Publications/2009/OFR09_4/index.html

Kuniansky, E.L. and Shoemaker, W.B., 2009, Conduit Flow Process (CFP) for MODFLOW-2005: in Proceedings 15th International Congress of Speleology, Kerrvile, Texas, USA, July 19-26, 2009; William B. White, ed.: Greyhound Press, Huntsville, Alabama: pp. 1568-1574.

Reimann, T. and Hill, M. E., 2009, MODFLOW-CFP: A New Conduit Flow Process for MODFLOW-2005: Ground Water, v. 47, p. 321-325. doi: 10.1111/j.1745-6584.2009.00561.x

Kuniansky, E.L., Halford, K.J., and Shoemaker, W.B., 2008, Permeater data verify new turbulence process for MODFLOW: Ground Water v. 46, no. 5, p. 768-771.

Shoemaker, W. B., K. J. Cunningham, E. L. Kuniansky, and J. Dixon, 2008, Effects of turbulence on hydraulic heads and parameter sensitivities in preferential groundwater flow layers: Water Resour. Res., 44, W03501, doi:10.1029/2007WR006601.

Hill, M.E., Martin, Angel, Stewart, M.T., 2008, Performance Evaluation of the Modflow-2005 Conduit Flow Process Applied to a Karst Aquifer Underlying West-Central Florida, inE. L. Kuniansky, editor, U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, p.93-98. http://pubs.usgs.gov/sir/2008/5023/37hill.htm

Shoemaker, W.B. and Kuniansky, E.L., 2008, Effects of Turbulence on Hydraulic Heads and Parameter Sensitivities in Preferential Ground-Water Flow Layers, in E. L. Kuniansky, editor, U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, p. 89-90. http://pubs.usgs.gov/sir/2008/5023/34shoemaker.htm

Kuniansky, E.L., Halford, K.J., and Shoemaker, W.B., 2008, Simulation of Turbulent Ground-Water Flow with MODFLOW-2005-Overview, in E. L. Kuniansky, editor, U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008: U.S. Geological Survey Scientific Investigations Report 2008-5023, p. 87-88. http://pubs.usgs.gov/sir/2008/5023/33kuniansky.htm

Shoemaker, W.B., Kuniansky, E.L., Birk, Steffen, Bauer, Sebastian, and Swain, E.D., 2008, Documentation of a Conduit Flow Process (CFP) for MODFLOW-2005: U.S. Geological Survey Techniques and Methods 6-A24, 50 p. http://pubs.usgs.gov/tm/tm6a24/

Shoemaker, W.B. and Kuniansky, E.L., 2007, Simulating Laminar and Turbulent Groundwater Flow in Fractured or Carbonate Aquifers: Geological Society of America abstracthttp://gsa.confex.com/gsa/2007AM/finalprogram/abstract_124784.htm