OGS

The van Genuchten capillary pressure model.
The van Genuchten capillary pressure model ([40]) is:
\[p_c(S)=p_b (S_\text{eff}^{1/m}1)^{1m}\]
with effective saturation defined as
\[S_\text{eff}=\frac{SS_r}{S_{\text{max}}S_r}.\]
Above, \(S_r\) and \(S_{\text{max}}\) are the residual and the maximum saturations. The exponent \(m \in (0,1)\) and the pressure scaling parameter \(p_b\) (it is equal to \(\rho g/\alpha\) in original publication) are given by the user. The scaling parameter \(p_b\) is given in same units as pressure.
In the original work another exponent \(n\) is used, but usually set to \(n = 1 / (1  m)\), and also in this implementation.
The the capillary pressure is computed from saturation as above but is cut off at maximum capillary pressure given by user.
No additional info.
Used in no endtoend test cases.