Soil-water evaporation is a complex multiphase phenomenon that is dependent on atmospheric demand, soil thermal and hydraulic properties, and internal transport mechanisms. Many of these aspects are still poorly understood and as a result many assumptions must be made and empirical formulations employed. One goal of our research is to test and develop different non-equilibrium phase change (i.e., evaporation and condensation) formulations in order to more realistically represent the actual physics of phase change and remove the need of an empirical diffusion enhancement factor that has no physical meaning. Experimental datasets used to test these formulations are generated in laboratory scale soil columns interfaced to a miniature wind tunnel. Measurements are made using a variety of different sensor technologies such as heat-pulse sensors and infrared radiometers.
Another of our research focuses on the impacts of atmospheric conditions (i.e., radiation, temperature, relative humidity, air flow) on soil-water evaporation rates. Temperature (-4.4 – 30°C) and relative humidity (5-95%) boundary conditions are carefully controlled and varied in a climate controlled closed circuit wind tunnel to which soil tanks are interfaced. The impacts of heterogeneity with respect to preferential flow and the suppressing or enhancement of evaporation under these boundary conditions in laboratory scale tanks up to 7.3 m in length. This provides invaluable information regarding upscaling to field-scales. The effects of turbulent air flow (0.8-10 m s-1 free stream velocity) are also studied using the wind tunnel /porous media test facility. Velocity profiles and two dimensional eddy structure precision experimental data are measured using a laser doppler velocitimetry system.