Effects of hydrophobicity on splash erosion of model soil particles by a single water drop impact
Effects of hydrophobicity on splash erosion of model soil particles by a single water drop impact
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DOI：
10.1002/esp.3364
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发表时间：
2013-09-15
影响因子：
3.3
通讯作者：
Shirtcliffe, Neil J.
中科院分区：
文献类型：
--
作者：
Ahn, Sujung;Doerr, Stefan H.;Shirtcliffe, Neil J.
雨滴的影响是土壤和其他颗粒材料的颗粒动员的主要因素。在以前的工作中，由疏水颗粒组成的疏水土壤在多次水滴冲击下表现出更大的飞溅侵蚀损失。然而，迄今为止，疏水和亲水颗粒表面在飞溅行为方面的基本原理差异尚未得到研究。在这项研究中，粒子疏水性对单个水滴撞击飞溅行为的影响采用高速摄像技术进行了检测。将直径为4mm的水滴滴在亲疏水玻璃珠（筛分范围350-400 μ m）床上，作为土壤模型颗粒。撞击时的落点速度为2.67ms(-1)，相当于类似大小雨滴末端速度的30%。由此产生的冲击行为是根据从床中喷出的粒子的轨迹和它们的最终静止位置来测量的。亲水粒子和疏水粒子对冲击水滴的响应在距离分布、粒子移动的中位数距离和喷射粒子的数量上有显著差异。疏水粒子喷射距离的增大主要是由于初始速度的增大而非喷射角度的差异。疏水颗粒的抛射轨迹比亲水颗粒高，抛射轨迹长，说明颗粒的疏水性从降雨侵蚀的初始阶段就开始影响溅射侵蚀，直到雨滴积聚形成水层。疏水颗粒的平均飞溅距离比亲水颗粒增加了10%，这表明颗粒的疏水性会导致更大的净侵蚀速率，这将在斜坡表面被放大，例如，在耕作的农业土壤或因砍伐或野火造成植被损失的山坡上的山脊。版权所有：John Wiley & Sons， Ltd。
Raindrop impact can be a major contributor to particle mobilization for soils and other granular materials. In previous work, water repellent soils, comprised of hydrophobic particles, have been shown to exhibit greater splash erosion losses under multiple drop impact. However, the underlying principle differences in splash behavior between hydrophobic and hydrophilic granular surfaces have not been studied to date. In this study the effects of particle hydrophobicity on splash behaviour by a single water drop impact were examined using high-speed videography. Water drops (4mm in diameter) were dropped on beds of hydrophilic and hydrophobic glass beads (sieved range: 350-400 mu m), serving as model soil particles. The drop velocity on impact was 2.67ms(-1), which corresponds to similar to 30% of the terminal velocity of a raindrop of similar size. The resulting impact behaviour was measured in terms of the trajectories of particles ejected from the beds and their final resting positions. The response to the impacting water drop was significantly different between hydrophilic and hydrophobic particles in terms of the distance distribution, the median distance travelled by the particles and number of ejected particles. The greater ejection distances of hydrophobic particles were mainly the result of the higher initial velocities rather than differences in ejecting angles. The higher and longer ejection trajectories for hydrophobic particles, compared with hydrophilic particles, indicate that particle hydrophobicity affects splash erosion from the initial stage of rainfall erosion before a water layer may be formed by accumulating drops. The similar to 10% increase in average splash distance for hydrophobic particles compared with hydrophilic particles suggests that particle hydrophobicity can result in greater net erosion rate, which would be amplified on sloping surfaces, for example, by ridges in ploughed agricultural soils or hillslopes following vegetation loss by clearing or wildfire. Copyright (c) 2012 John Wiley & Sons, Ltd.