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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The grain size dependency of vesicular particle shapes strongly affects the drag of particles. First results from microtomography investigations of Campi Flegrei fallout deposits
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The grain size dependency of vesicular particle shapes strongly affects the drag of particles. First results from microtomography investigations of Campi Flegrei fallout deposits

机译：囊泡颗粒形状的粒度依赖性强烈影响颗粒的阻力。 Campi Flegrei沉淀沉积物显微照相调查的初步结果

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摘要

Acknowledging the grain size dependency of shape is important in volcanology, in particular when dealing with tephra produced and emplaced during and after explosive volcanic eruptions. A systematic measurement of the tridimensional shape of vesicular pyroclasts of Campi Flegrei fallout deposits (Agnano-Monte Spina, Astroni 6 and Averno 2 eruptions) varying in size from 8.00 to 0.016 mm has been carried out by means of X-Ray Microtomography. Data show that particle shape changes with size, especially for juvenile vesicular clasts, since it is dependent on the distribution and size of vesicles that contour the external clast outline. Two drag laws that include sphericity in the formula were used for estimating the dependency of settling velocity on shape. Results demonstrate that it is not appropriate to assume a size-independent shape for vesicular particles, in contrast with the approach commonly employed when simulating the ash dispersion in the atmosphere. (C) 2018 Elsevier B.V. All rights reserved.
机译：认识到形状对晶粒大小的依赖性在火山学中很重要，特别是在处理火山爆发期间和之后产生和安置的提菲拉时。通过X射线显微断层摄影术，系统地测量了Campi Flegrei沉积沉积物（Agnano-Monte Spina，Astroni 6和Averno 2喷发）的囊泡裂殖体的三维形状，尺寸从8.00到0.016 mm不等。数据表明，颗粒形状随大小而变化，尤其是对于幼小囊泡，因为它取决于轮廓外部囊泡轮廓的囊泡的分布和大小。公式中包括球形的两个阻力定律用于估计沉降速度对形状的依赖性。结果表明，与模拟大气中灰分分散的常用方法相反，对于泡状颗粒采用大小无关的形状是不合适的。 （C）2018 Elsevier B.V.保留所有权利。

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