Effects of some surfactants on foliar impaction and retention of monosize water droplets

✍ Scribed by Webb, Duncan A; Holloway, Peter J; Western, Nigel M

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 227 KB
• Volume: 55
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199903)55:3<382::aid-ps920>3.0.co;2-f

✦ Synopsis

The impaction and retention behavior of low-velocity (below 3 m s-1) monosize droplets (100-1000 lm diameter) containing either water or aqueous surfactant solutions was examined on wettable and water-repellant leaf surfaces using a high magniücation video system. Mapping of bounce trajectories provided a history of droplet behaviour from ürst impact to ünal retention on, or escape from, a leaf, and yielded velocity thresholds for capture or bounce following impact of any droplet. Water droplets were captured on water-repellant leaves only when their pre-impact velocity fell below 0.25 m s-1, so that even small (120 lm) lowvelocity (0.57 m s-1) droplets bounced between two and six times before ünally being retained. Surfactant addition invariably reduced the number of bounces between ürst impact and retention, and increased the velocity threshold for capture following impact. The physical parameters of droplets, as expressed by Reynolds (Re) and Weber (We) numbers, are discussed and the trajectory data shown to generate two relationships between Re and We which deüne the transition from capture to bounce following impact.