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OGS
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OGS
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The Penman-Millington-Quirk (PMQ) Vapour diffusion model.
The vapour diffusion can be described by [28], [29],
\[ D_v=D_0 \left(\frac{T}{273.15}\right)^{n} D_{vr}, \]
where \(D_{0}\) is the base diffusion coefficient with default value \(2.16\cdot 10^{-5}\) \({\text m}^2 \text{Pa}/(\text{s}\text{K}^{n})\), \(n\) is the exponent with default value 1.8, \(D_{vr}\) is the the relative diffusion coefficient, and \(T\) is the temperature.
The Penman–Millington–Quirk (PMQ) model [28] is given as
\[ D_{vr}=0.66 \phi \left(\frac{\kappa}{\phi}\right)^{\frac{12-m}{3}}, \]
where \(\phi\) is the total porosity, \(\kappa\) is the air filled porosity, and \(m\) is a fitting parameter. The air filled porosity is defined as \( \kappa = \phi-\theta = \phi -S_L \phi \) with \(\theta\) the liquid content, and \(S_L\) the liquid saturation.
According to the study presented in [28], \(m=6\) is the best fitting parameter for the sieved, repacked soils that the authors tested. Therefore, \(m=6\) is used in the implementation, which gives
\[ D_{vr}=0.66 \phi (1 - S_L )^2. \]
Note: In order to maintain consistency with the implementation of the computations of other vapor-related parameters, \( \phi (1 - S_L )\) is removed from the implementation for this class and is multiplied back in the local assembler.
Used in no end-to-end test cases.
1.12.0