- CBW's C parameter. Must be > 1. Typical value would be 1.05.
C++ Type:double

Description:BW's C parameter. Must be > 1. Typical value would be 1.05.

- SnLow saturation. This must be < Ss, and non-negative. This is BW's initial effective saturation, below which effective saturation never goes in their simulations/models. If Kn=0 then Sn is the immobile saturation. This form of effective saturation is only correct for Kn small.
C++ Type:double

Description:Low saturation. This must be < Ss, and non-negative. This is BW's initial effective saturation, below which effective saturation never goes in their simulations/models. If Kn=0 then Sn is the immobile saturation. This form of effective saturation is only correct for Kn small.

- lasBW's lambda_s parameter multiplied by (fluid_density * gravity). Must be > 0. Typical value would be 1E5
C++ Type:double

Description:BW's lambda_s parameter multiplied by (fluid_density * gravity). Must be > 0. Typical value would be 1E5

# PorousFlowCapillaryPressureBW

Broadbridge and White capillary pressure for negligable Kn

The Broadbridge-White capillarity relationship valid for small is (Broadbridge and White, 1988) (1) where (2) and is the Lambert W-function that satisfies . This is of limited use in real simulations, and is only used in the Porous Flow module for comparison with the analytical solutions of Broadbridge and White (1988) and Warrick et al. (1990) for multi-phase infiltration and drainage problems.

Only effective saturation as a function of capillary pressure is available

## Input Parameters

- Ss1High saturation. This must be > Sn and <= 1. Effective saturation where porepressure = 0. Effective saturation never exceeds this value in BW's simulations/models.
Default:1

C++ Type:double

Description:High saturation. This must be > Sn and <= 1. Effective saturation where porepressure = 0. Effective saturation never exceeds this value in BW's simulations/models.

- pc_max1e+09Maximum capillary pressure (Pa). Must be > 0. Default is 1e9
Default:1e+09

C++ Type:double

Description:Maximum capillary pressure (Pa). Must be > 0. Default is 1e9

- sat_lr0Liquid residual saturation. Must be between 0 and 1. Default is 0
Default:0

C++ Type:double

Description:Liquid residual saturation. Must be between 0 and 1. Default is 0

- log_extensionTrueUse a logarithmic extension for low saturation to avoid capillary pressure going to infinity. Default is true. Set to false if your capillary pressure depends on spatially-dependent variables other than saturation, as the log-extension C++ code for this case has yet to be implemented
Default:True

C++ Type:bool

Description:Use a logarithmic extension for low saturation to avoid capillary pressure going to infinity. Default is true. Set to false if your capillary pressure depends on spatially-dependent variables other than saturation, as the log-extension C++ code for this case has yet to be implemented

- blockThe list of block ids (SubdomainID) that this object will be applied
C++ Type:std::vector

Description:The list of block ids (SubdomainID) that this object will be applied

### Optional Parameters

- enableTrueSet the enabled status of the MooseObject.
Default:True

C++ Type:bool

Description:Set the enabled status of the MooseObject.

- allow_duplicate_execution_on_initialFalseIn the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
Default:False

C++ Type:bool

Description:In the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).

- use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.
Default:False

C++ Type:bool

Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

- control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector

Description:Adds user-defined labels for accessing object parameters via control logic.

- seed0The seed for the master random number generator
Default:0

C++ Type:unsigned int

Description:The seed for the master random number generator

- implicitTrueDetermines whether this object is calculated using an implicit or explicit form
Default:True

C++ Type:bool

Description:Determines whether this object is calculated using an implicit or explicit form

### Advanced Parameters

## Input Files

- modules/porous_flow/test/tests/broadbridge_white/bw02.i
- modules/porous_flow/test/tests/broadbridge_white/wli01.i
- modules/porous_flow/test/tests/jacobian/fflux10.i
- modules/porous_flow/test/tests/broadbridge_white/wli02.i
- modules/porous_flow/test/tests/broadbridge_white/bw01.i

## References

- P. Broadbridge and I. White.
Constant rate rainfall infiltration: a versatile nonlinear model, 1. analytical solution.
*Water Resources Research*, 24:145–154, 1988.[BibTeX] - A. W. Warrick, D. O. Lomen, and A. Islas.
An analytical solution to Richards' Equation for a Draining Soil Profile.
*Water Resources Research*, 26:253–258, 1990.[BibTeX]