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OGS
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The van Genuchten capillary pressure model.
The van Genuchten capillary pressure model ([42]) is:
p_c(S)=p_b (S_\text{eff}^{-1/m}-1)^{1-m}
with effective saturation defined as
S_\text{eff}=\frac{S-S_r}{S_{\text{max}}-S_r}.
Above, S_r and S_{\text{max}} are the residual and the maximum saturations. The (pressure) 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.
Another (saturaton) exponent n is usually set to n = 1 / (1 - m).
The saturation is computed from the capillary pressure as follows:
S(p_c)= \begin{cases} S_{\text{max}} & \text{for $p_c \leq 0$, and}\\ \left( \left(\frac{p_c}{p_b}\right)^{\frac{1}{1-m}} +1\right)^{-m} (S_{\text{max}}-S_r) +S_r& \text{for $p_c > 0$.} \end{cases}
The result is then clamped between the residual and maximum liquid saturations.
Either the exponent (which is the pressure exponent m in the equations) must be set and then the saturation exponent is n = 1 / (1 - m). Or both values the pressure_exponent and the saturation_exponent must be set independently.
No additional info.
1.12.0