The Role of Wind Velocity in Saline Water Evaporation from Porous Media and Surface Salt Crystallization Dynamics

Abstract

This study systematically investigates the effect of wind flow on evaporation dynamics and salt crystallization patterns in porous media. Well-controlled experiments were conducted in a laboratory wind tunnel, where the surface of sand columns saturated with freshwater and NaCl solutions at concentrations of 10%, 15%, and 20% were subjected to wind flows of 0.5 and 5 m/s, corresponding to laminar and turbulent flow regimes, respectively. Mass loss measurements from the samples, combined with optical imaging of their surfaces, revealed distinct evaporation dynamics and crystallization patterns. We observed that the interaction between intermittent turbulent airflow and evolving salt crystals on the surface resulted in a relatively uniform crystallization pattern. In contrast, under laminar airflow conditions, salt crystal nucleation and formation primarily occurred at the leading edge of the sample, particularly at lower salt concentrations. We further investigated the impact of enhanced evaporative mass loss in the presence of wind on crystallization dynamics by quantifying the crystal coverage and its lateral extent on the surface. Under turbulent flow conditions, we observed that full coverage of the surface with salt crystals requires 2 to 3 times higher evaporative losses in 10% NaCl sample relative to the 15% and 20% samples, respectively. These findings highlight the complex interplay between evaporation and crystallization processes under varying airflow conditions, thus offering valuable insight for improving hydrological and climatological modeling.