Time: |
January 18, 2011 |
Lecturer: |
Ebrahim Shahraeeni
Soil and Terrestrial Environmental Physics (STEP), ETH Zürich |
Venue: |
Pfaffenwaldring 61, Raum U1.003 (MML), Universität Stuttgart
|
Download as iCal: |
|
Prediction of evaporation from porous media remains a challenge due to the interactions betweenenergy and atmospheric conditions (radiation, humidity, temperature, air velocity) andporous medium properties often resulting in abrupt transitions and complex dynamics. On theinterface of an evaporative porous medium there is a coupled mass and energy transfer problemdefines vapor flux from wet pores across atmospheric boundary layer and temporal variationsof the surface wetness which dynamically feeds back to the transfer problem and specifiesthe instantaneous exchange rates. To quantify the coupling between soil and atmosphere,a pore scale analysis has been developed to simulate the variations of surface water content inthe course of evaporation and link it to the transport properties of the interface across theboundary layer. Such a model provides the possibility for the simulation of a transient evaporationprocess starting from a fully saturated surface and dried out to the stage II of evaporationshowing a continuous decrease in evaporation flux reminiscent of internal diffusion controlprocess while capillary flow continuously supplies the vaporization surface. The simulationresults are consistent with the experiments conducted in the wind tunnel under controlledboundary conditions. A systematic method for infrared thermography of an evaporative surfacein the wind tunnel will also be presented which gives spatial and temporal data for massand energy exchange at pore scale and could verify the model accuracy providing the necessarybuilding block for the field scale studies of interaction between partially wet terrestrialsurfaces and atmosphere during evaporation.