Drop size dependence of soil-water contact angle in relation to the droplet geometry and line tension(Soil physics)

スポンサーリンク

概要

• 論文の詳細を見る

• The soil-water contact angle is used as a measure of the surface hydrophobicity of soils. The contact angle for particular solid-liquid combination is considered to vary with the drop size. In this paper, we focused on examining the drop size dependence of contact angle on soil surfaces compared with homogeneous solid surfaces, and determining its relation to the droplet geometry and line tension. The contact angle estimated using geometric parameters of the droplets (θ_G) showed decreasing trend with increasing drop size from 5 to 50μL irrespective of the deformations in the droplet shape in larger drops. This was considered to be a result of the corresponding deviations of the geometric parameters of the droplets. The directly measured contact angle (θ_A) first decreased and then increased with increasing drop size from 5 to 50μL. The drop size at lowest θ_A for hydrophobized silica sand with 1gkg^<-1> stearic acid (SA) and the acryl surfaces was 20μL, whereas that for hydrophobized silica sand with 5gkg^<-1> SA and siliconed paper was 30μL. The decrease in θ_A with increasing drop size was explained as a result of the line tension effect using the modified Young's equation. Despite the surface heterogeneity, all the surfaces tested in this study showed positive line tensions on the order of 10μJm^<-1>. Irrespective of the heterogeneity of the surfaces, the θ_A in this experiment agreed with the modified Young's equation for drop sizes up to about 20-30μL, where the θ_A and θ_G were also in good agreement. Drop size dependence of contact angle was independent of the level of surface hydrophobicity. The θ_A on all the examined surfaces started to increase with increasing drop size when the deformation index, I_d, exceeded 5%, where the wetting radius, R exceeded the capillary length. The increase in θ_A with increasing drop size was attributed to the deformations of water drops due to the effect of gravity.

• 2012-12-00

著者

• Karube Jutaro

  Faculty Of Agriculture Ibaraki University

• Leelamanie Dewpura

  Faculty Of Agriculture University Of Ruhuna

• LEELAMANIE Dewpura

  Faculty of Agriculture, University of Ruhuna:Faculty of Agriculture, Ibaraki University

関連論文

• Effects of hydrophobic and hydrophilic organic matter on the water repellency of model sandy soils(Soil Physics)
• Time dependence of contact angle and its relation to repellency persistence in hydrophobized sand(Soil Physics)
• Relative humidity effects on contact angle and water drop penetration time of hydrophobized fine sand(Soil Physics)
• Characterizing water repellency indices : Contact angle and water drop penetration time of hydrophobized sand(Soil Physics)
• Effects of organic compounds, water content and clay on the water repellency of a model sandy soil(Soil Physics)
• Clay effects on the contact angle and water drop penetration time of model soils(Soil Physics)
• Water-dependent repellency of model soils as affected by clay(Soil Physics)
• Drop size dependence of soil-water contact angle in relation to the droplet geometry and line tension(Soil physics)
• Soil-water contact angle as affected by the aqueous electrolyte concentration(Soil physics)
• Stability analysis of aggregates in relation to the hydrophobicity of organic manure for Sri Lankan Red Yellow Podzolic soils(Soil physics)

スポンサーリンク