Nonlinear Analysis of Heat and Moisture Transer in Unsaturated Soil

The nonlinear analysis of heat and moisture transfer in partly saturated soil is discussed. A numerical solution of a theoretical formulation derived by the writer is presented. The method allows the nonlinear nature of the soil parameters to be modeled for the first time. The prediction of the coupled transient behavior of several interrelated phenomena is consequently achieved. The algorithm employed consists of a finite element spatial solution procedure coupled with a finite difference time‐stepping scheme. The one‐dimensional application of the model is illustrated with reference to the problem of a soil stratum that is subjected to surface evaporative soil moisture losses. The results obtained reveal the complex pattern of moisture migration that can occur in practice, with moisture transfer taking place simultaneously in two opposite directions. The importance of thermal‐induced flow is demonstrated, together with the influence of the nonlinearities in the soil diffusivities.