文章基本信息

标题：Effect of particle volume fraction on the settling velocity of volcanic ash particles: insights from joint experimental and numerical simulations
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作者：Elisabetta Del Bello ; Jacopo Taddeucci ; Mattia de’ Michieli Vitturi 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2017
卷号：7
页码：39620
DOI：10.1038/srep39620
语种：English
出版社：Springer Nature
摘要：Most of the current ash transport and dispersion models neglect particle-fluid (two-way) and particle-fluid plus particle-particle (four-way) reciprocal interactions during particle fallout from volcanic plumes. These interactions, a function of particle concentration in the plume, could play an important role, explaining, for example, discrepancies between observed and modelled ash deposits. Aiming at a more accurate prediction of volcanic ash dispersal and sedimentation, the settling of ash particles at particle volume fractions ( ϕ _p) ranging 10⁻⁷-10⁻³ was performed in laboratory experiments and reproduced by numerical simulations that take into account first the two-way and then the four-way coupling. Results show that the velocity of particles settling together can exceed the velocity of particles settling individually by up to 4 times for ϕ _p ~ 10⁻³. Comparisons between experimental and simulation results reveal that, during the sedimentation process, the settling velocity is largely enhanced by particle-fluid interactions but partly hindered by particle-particle interactions with increasing ϕ _p. Combining the experimental and numerical results, we provide an empirical model allowing correction of the settling velocity of particles of any size, density, and shape, as a function of ϕ _p. These corrections will impact volcanic plume modelling results as well as remote sensing retrieval techniques for plume parameters.