Ali Chaudhry, SFB 1313 doctoral researcher at the Forschungszentrum Jülich (research project C05), will give his milestone presentation on "Non-Invasive Imaging of Solute Redistribution and Salt Precipitation During Evaporation from Porous Media" on 26 November 2024.
Date: Tuesday, 26 November 2024
Time: 2 pm CET
Title: "Non-Invasive Imaging of Solute Redistribution and Salt Precipitation During Evaporation from Porous Media"
Place: Online presentation. If you are interested in Ali Chaudhry's milestone presentation, please contact Samaneh Vahid Dastjerdi to receice the Webex link >>> samaneh.vahiddastjerdi@mechbau.uni-stuttgart.de
Abstract
Evaporation from porous media is a key phenomenon in the terrestrial environment and is linked to accumulation of solutes at or near the evaporative surface. It eventually leads to salinized soil and weathering of building materials, topics with high economic impact. In this context, the current study aims at the understanding of solute accumulation near evaporating surfaces for model porous media at the cm-scale. Analytical and numerical modelling predict the development of local instabilities due to density differences during evaporation in case of saturated porous media with high permeability. This eventually causes density-driven backflow through fingering. To experimentally investigate this process, we performed experiments on sand packings with two types of porous media: F36 (medium sand) and W3 (fine sand/silt) with porosities of 0.37 and 0.39, respectively. The intrinsic permeability of the two packings differed by two orders of magnitude. Using magnetic resonance imaging (23Na-MRI), we successfully monitored the development of solute accumulation and subsequent backflow during evaporation with a continuous supply of water at the bottom of the samples (wicking conditions). With implications for time to crust formation, we performed further experiments with the control of wind velocity using a wind tunnel and an array of sand packings. Time to crust formation was significantly different for sands with different particle sizes and permeabilities undergoing similar evaporation rates. With these findings we aim to understand this dynamic process in a heterogeneous sand packing arrangement through further investigations using MRI and X-ray computed tomography.