A Simulation Study of the Drying-Front Phenomenon

ABSTRACTA simulation technique, using CSMP language, was designed to study the possible influence of different diffusivity-water content relations on the shape of the soil moisture profile during profile-controlled evaporation. Only the use of a “hooked” diffusivity function (which takes into account the increase in vapor diffusivity in the dry range) resulted in an inflected soil moisture profile, with the inflection point propagating into the soil with the square root of time. Cumulative evaporation was slightly higher in this case than in the cases where the diffusivity continued to decrease, or leveled out, in the dry range. The analysis assumed infinite external evaporativity, and isothermal and homogeneous soil conditions with no gravity or internal drainage effects. A simulation technique, using CSMP language, was designed to study the possible influence of different diffusivity-water content relations on the shape of the soil moisture profile during profile-controlled evaporation. Only the use of a “hooked” diffusivity function (which takes into account the increase in vapor diffusivity in the dry range) resulted in an inflected soil moisture profile, with the inflection point propagating into the soil with the square root of time. Cumulative evaporation was slightly higher in this case than in the cases where the diffusivity continued to decrease, or leveled out, in the dry range. The analysis assumed infinite external evaporativity, and isothermal and homogeneous soil conditions with no gravity or internal drainage effects.