Water repellent soils, or hydrophobic soils, are described as having delayed wetting of the soil surface and reduced amount of water infiltration, which has been proposed as alternative slope cover materials. The degree of soil water repellency is usually judged by the droplet interaction with the soil surface in the experimental studies. Hence, in this study, the potential capability of the Lattice Boltzmann (LB) method in studying the droplet dynamics on a granular surface with varying wettability is demonstrated, of which the implications to characterizing the soil water repellency are discussed. Simulations are performed on the droplet standing, infiltrating and sliding. On a horizontal surface, LB method can be used to interpret the intrinsic contact angle (CA) at the particle level by simulating the droplet standing with an apparent CA or the time for a droplet to infiltrate. On an inclined surface, LB method helps seek the critical combination of CA and slope angle to trigger the droplet movement, which prevents the accumulation of water on a slope. Therefore, performing the LB simulations within those scenarios will reveal the performance of the water repellent soils in resisting the water infiltration.
Soil water repellency Droplet dynamics Lattice boltzmann
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This work has been funded by the General Research Fund, Research Grants Council of Hong Kong (17203417: Physically-enhanced water repellency in granular materials). This simulation is conducted in part using the HKU ITS research computing facilities that are supported in part by the Hong Kong UGC Special Equipment Grant (SEG HKU09).
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