Browsing by Author "Kim, Seungho"

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    Mechanics of removing water from the ear canal: Rayleigh-Taylor instability
    Kim, Seungho; Baskota, Anuj; Kang, Hosung; Jung, Sunghwan (Cambridge University Press, 2023-05)
    Water stuck in the ear is a common problem during showering, swimming or other water activities. Having water trapped in the ear canal for a long time can lead to ear infections and possibly result in hearing loss. A common strategy for emptying water from the ear canal is to shake the head, where high acceleration helps remove the water. In this present study, we rationalize the underlying mechanism of water ejection/removal from the ear canal by performing experiments and developing a stability theory. From the experiments, we measure the critical acceleration to remove the trapped water inside different sizes of canals. Our theoretical model, modified from the Rayleigh-Taylor instability, can explain the critical acceleration observed in experiments, which strongly depends on the radius of the ear canal. The resulting critical acceleration tends to increase, especially in smaller ear canals, which indicates that shaking heads for water removal can be more laborious and potentially threatening to children due to their small size of the ear canal compared with adults.
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    Vortex-induced dispersal of a plant pathogen by raindrop impact
    Kim, Seungho; Park, Hyunggon; Gruszewski, Hope A.; Schmale, David G. III; Jung, Sunghwan (NAS, 2019)
    Raindrop impact on infected plants can disperse micron-sized propagules of plant pathogens (e.g., spores of fungi). Little is known about the mechanism of how plant pathogens are liberated and transported due to raindrop impact.We used high-speed photography to observe thousands of dry-dispersed spores of the rust fungus Puccinia triticina being liberated from infected wheat plants following the impact of a single raindrop.We revealed that an air vortex ring was formed during the raindrop impact and carried the dry-dispersed spores away from the surface of the host plant. The maximum height and travel distance of the airborne spores increased with the aid of the air vortex. This unique mechanism of vortex-induced dispersal dynamics was characterized to predict trajectories of spores. Finally, we found that the spores transported by the air vortex can reach beyond the laminar boundary layer of leaves, which would enable the long-distance transport of plant pathogens through the atmosphere.