Simulation of water flow and heat transfer in soils by means of a mixed finite element method

We develop numerical methods for the simulation of heat and mass transfer i n the ground. We use the mixed finite element method for the computation of both the liquid pressure and the temperature, so that the mass is locally and globally well conserved and the computation of the fluid velocity is ve ry accurate. This is quite important since this fluid velocity appears in t he first-order term of the equation for the temperature; in turn the partia lly hyperbolic character of the equation for the temperature is well taken into account since we use the modified method of characteristics for its di scretization. (C) 1999 Elsevier Science Ltd. All rights reserved.