The Penman-Millington-Quirk (PMQ) Vapour diffusion model.

The vapour diffusion can be described by [27], [28],

\[ D_v=D_0 \left(\frac{T}{273.15}\right)^{n} D_{vr}, \]

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 [27] 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 [27], \(m=6\) 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.

Child parameters, attributes and cases

Additional info

Used in the following test data files