In the previous sections, the transport equations for the liquid and the vapor phases were considered separately (Eqs. (27) and (47)). To get a complete description of the transport, both equations should be added together:
This is Richards' equation. As can be seen, the equation fully describes the movement of both vapor and liquid water on the basis of a single variable
θL. The influence of both phases is taken into account through the function
Dθ, which contains a term associated to the vapor transport and a second one related to the transport of the liquid phase. The demonstration also indicates that the variable
θ of the original Eq.
(4) stands for the volumetric liquid water content, which is expressed in cubic meter of water per cubic meter of material.
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Water transport Previous:
Transport of water
and θG≈θL, Eq.
(48) can be simplified as:
