What is it about?
The impact of multiple adjacent droplets on solid surfaces is a common phenomenon observed in nature, such as raindrop impacts on plant leaves or car windshields, and in industrial and agricultural spray processes like spray cooling, spray painting and pesticide spraying. These processes involve non-simultaneous droplet impacts, where droplets strike the surface with time lags. We investigate these ubiquitous yet little-understood impacts, focusing on how adjacent droplets interact and the resulting liquid spreading and splashing behaviour, providing new insights into the underlying dynamics.
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Why is it important?
Most studies on the physics of liquid droplets impacting surfaces have focused on single-droplet impacts, even though multiple-droplet impacts are more prevalent in real-world scenarios. When two adjacent droplets interact upon their impacts, they can produce an uprising liquid sheet that significantly alters the outcomes compared to single-droplet impacts. This sheet can become unstable and generate liquid fragments, whereas a single droplet would simply deposit on the surface without fragmenting. Understanding the physics behind these interactions and the resultant fragmentation during multiple-droplet impacts is essential for optimizing spray-based applications. Furthermore, it is conducive to understanding pathogen transmission through the fragmented droplets generated upon droplet impacts on contaminated surfaces.
Perspectives
This study provides the first detailed characterization of the ubiquitous yet poorly understood non-simultaneous multiple-droplet impacts on solid surfaces, introducing novel scaling laws. Its comprehensive analysis establishes a foundational framework for future research on multi-droplet impacts, which is essential for understanding dense spray processes that go beyond single-droplet models.
Dr Anjan Goswami
Imperial College London
Read the Original
This page is a summary of: Non-simultaneous impact of droplet pairs on solid surfaces, Physics of Fluids, September 2024, American Institute of Physics,
DOI: 10.1063/5.0225562.
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