Taraprasad Bhowmick, Yong Wang, Jonas Latt, Gholamhossein Bagheri
{"title":"Twist, turn and encounter: the trajectories of small atmospheric particles unravelled","authors":"Taraprasad Bhowmick, Yong Wang, Jonas Latt, Gholamhossein Bagheri","doi":"arxiv-2408.11487","DOIUrl":null,"url":null,"abstract":"Every solid particle in the atmosphere, from ice crystals and pollen to dust,\nash, and microplastics, is non-spherical. These particles play significant\nroles in Earth's climate system, influencing temperature, weather patterns,\nnatural ecosystems, human health, and pollution levels. However, our\nunderstanding of these particles is largely based on the theories for extremely\nsmall particles and experiments conducted in liquid mediums. In this study, we\nused an innovative experimental setup and particle-resolved numerical\nsimulations to investigate the behaviour of sub-millimetre ellipsoids of\nvarying shapes in the air. Our results revealed complex decaying oscillation\npatterns involving numerous twists and turns in these particles, starkly\ncontrasting their dynamics in liquid mediums. We found that the frequency and\ndecay rate of these oscillations have a strong dependence on the particle\nshape. Interestingly, disk-shaped particles oscillated at nearly twice the\nfrequency of rod-shaped particles, though their oscillations also decayed more\nrapidly. During oscillation, even subtly non-spherical particles can drift\nlaterally up to ten times their volume-equivalent spherical diameter. This\nbehaviour enables particles to sweep through four times more air both\nvertically and laterally compared to a volume-equivalent sphere, significantly\nincreasing their encounter rate and aggregation possibility. Our findings\nprovide an explanation for the long-range transport and naturally occurring\naggregate formation of highly non-spherical particles such as snowflakes and\nvolcanic ash.","PeriodicalId":501270,"journal":{"name":"arXiv - PHYS - Geophysics","volume":"256 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - PHYS - Geophysics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2408.11487","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Every solid particle in the atmosphere, from ice crystals and pollen to dust,
ash, and microplastics, is non-spherical. These particles play significant
roles in Earth's climate system, influencing temperature, weather patterns,
natural ecosystems, human health, and pollution levels. However, our
understanding of these particles is largely based on the theories for extremely
small particles and experiments conducted in liquid mediums. In this study, we
used an innovative experimental setup and particle-resolved numerical
simulations to investigate the behaviour of sub-millimetre ellipsoids of
varying shapes in the air. Our results revealed complex decaying oscillation
patterns involving numerous twists and turns in these particles, starkly
contrasting their dynamics in liquid mediums. We found that the frequency and
decay rate of these oscillations have a strong dependence on the particle
shape. Interestingly, disk-shaped particles oscillated at nearly twice the
frequency of rod-shaped particles, though their oscillations also decayed more
rapidly. During oscillation, even subtly non-spherical particles can drift
laterally up to ten times their volume-equivalent spherical diameter. This
behaviour enables particles to sweep through four times more air both
vertically and laterally compared to a volume-equivalent sphere, significantly
increasing their encounter rate and aggregation possibility. Our findings
provide an explanation for the long-range transport and naturally occurring
aggregate formation of highly non-spherical particles such as snowflakes and
volcanic ash.