Pore‐scale water dynamics during drying and the impacts of structure and surface wettability

• Published in: Water resources research 2017-07, Vol.53 (7), p.5585-5600
• Main Authors: Cruz, Brian C., Furrer, Jessica M., Guo, Yi‐Syuan, Dougherty, Daniel, Hinestroza, Hector F., Hernandez, Jhoan S., Gage, Daniel J., Cho, Yong Ku, Shor, Leslie M.
• Format: Article
• Language: English
• Subjects: Agglomeration; Aggregates; Aggregation; Computer simulation; Contact angle; Drying; Dynamics; ENGINEERING; Evaporation; Evaporation rate; Forces (mechanics); Groundwater flow; High water repellency micromodels dried 4 times slower than low water repellency micromodels regardless of aggregation A lattice Boltzmann model was developed and accurately reproduces pore-scale moisture distribution during evaporative drying Water film flow and meniscus shape are significant factors in reducing evaporative drying in high water repellency micromodels; lattice Boltzmann method; Loam; Loam soils; microfluidic; Microstructure; Moisture; Mucilage; Mucilages; Multiphase; Pest control; Pore size; Pore size distribution; Pores; Porosity; Repellency; Repellents; Retention; Rhizosphere; Sandy loam; Sandy soils; Saturation; Secretion; Size distribution; Soil; Soil aggregates; Soil conditions; Soil moisture; Soil structure; Soil water; Soil water movement; Soils; Spatial distribution; Stress concentration; unsaturated; Wettability
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1002/2016WR019862

Plants and microbes secrete mucilage into soil during dry conditions, which can alter soil structure and increase contact angle. Structured soils exhibit a broad pore size distribution with many small and many large pores, and strong capillary forces in narrow pores can retain moisture in soil aggregates. Meanwhile, contact angle determines the water repellency of soils, which can result in suppressed evaporation rates. Although they are often studied independently, both structure and contact angle influence water movement, distribution, and retention in soils. Here drying experiments were conducted using soil micromodels patterned to emulate different aggregation states of a sandy loam soil. Micromodels were treated to exhibit contact angles representative of those in bulk soil (8.4° ± 1.9°) and the rhizosphere (65° ± 9.2°). Drying was simulated using a lattice Boltzmann single‐component, multiphase model. In our experiments, micromodels with higher contact angle surfaces took 4 times longer to completely dry versus micromodels with lower contact angle surfaces. Microstructure influenced drying rate as a function of saturation and controlled the spatial distribution of moisture within micromodels. Lattice Boltzmann simulations accurately predicted pore‐scale moisture retention patterns within micromodels with different structures and contact angles. Key Points High water repellency micromodels dried 4 times slower than low water repellency micromodels regardless of aggregation A lattice Boltzmann model was developed and accurately reproduces pore‐scale moisture distribution during evaporative drying Water film flow and meniscus shape are significant factors in reducing evaporative drying in high water repellency micromodels