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OGS
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A model for water vapour density in the unsaturated porous media.
The water vapour density is given by
\rho_v = h\, \rho_{vS},
where h is the relative humidity according to
h=\exp \left({\frac{p}{\rho_w R T}}\right),
with R the specific gas constant for water vapour, and \rho_{vS}, is the saturated vapour density given by
\rho_{vS}=10^{-3}\, \exp({19.819-4975.9/T}).
The specific gas constant for water vapour R=461.6\,\text{J}\,\text{kg}^{-1}\text{K}^{-1}, the value is calculated by R_g/M_w with R_g= 8.3144621\,\text{J}\,\text{mol}^{-1}\text{K}^{-1}, the ideal gas constant, and M_w=0.018016\,\text{kg}\,\text{mol}^{-1}, the molar mass of water.
The formula of this density model is presented on page 20 of [21].
In the application, the vapour density related terms in the mass balance equation are multiplied with 1-S with S , the water saturation. Therefore the application of the water vapour density model is naturally restricted in the unsaturated zones.
It belongs to vapour_density. That means the name of this property is vapour_density. Besides, it has no parameter to be input.
1.12.0