A new analytical scaling for turbulent wind-bent plumes: Comparison of scaling laws with analog experiments and a new database of eruptive conditions for predicting the height of volcanic plumes
A new analytical scaling for turbulent wind-bent plumes: Comparison of scaling laws with analog experiments and a new database of eruptive conditions for predicting the height of volcanic plumes
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DOI：
10.1016/j.jvolgeores.2017.07.006
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发表时间：
2017-09-01
影响因子：
2.9
通讯作者：
Dunning, Jack
中科院分区：
文献类型：
--
作者：
Aubry, Thomas J.;Jellinek, A. Mark;Dunning, Jack
各种比例关系将火山羽流的高度与喷发源条件、大气密度分层、湍流夹带和风应力联系起来。然而，用于测试这些比例的观察、模拟和数值研究仅捕获了狭窄范围的自然喷发条件。特别是，现有的分析尺度不适用于大多数火山喷发的典型风应力条件。因此，我们开发了一种新的分析尺度，用于测量密度分层均匀横流中上升的浮力羽流的高度。我们将此标度与现有的分析标度（Morton 等人，1956 年；Hewett 等人，1971 年）以及“功能”标度（即，表示为 Morton 等人（1956 年）标度函数的参数化和与风应力相关的状态参数、Degruyter 和 Bonadonna（2012 年）、Woodhouse 等人（2013 年）、Carazzo 等人（Carazzo 等人）进行了比较。 (2014)) 使用 Carazzo 等人的广泛实验数据集。 (2014) 以及来自新数据库的自然事件，包括 94 个喷发阶段。我们提出的缩放最好地预测了实验羽流的高度，这使我们能够限制风与径向夹带系数的比率。对于自然喷发，伍德豪斯等人。 （2013）和卡拉佐等人。 (2014) 缩放比例明确考虑了风梯度，可以最好地预测羽流高度。我们表明，考虑大气层结和风可以改善大规模喷发率和羽流高度之间的经验关系。对于测试的缩放比例，对自然喷发的剩余高度的分析支持了火山羽流在潮湿的大气中升得更高的假设。最后，对于在中度至高风应力下上升的模拟羽流，我们表明羽流形状随着羽流高度的变化而演变，违反了所有缩放和积分模型结果所依赖的自相似性假设。我们依次讨论放宽自相似性假设的后果以及标准积分羽流模型的潜在改进。 (C) 2017 Elsevier B.V. 保留所有权利。
Various scaling relationships relate the height of volcanic plumes to eruptive source conditions, atmospheric density stratification, turbulent entrainment, and wind stresses. However, observational, analog, and numerical studies used to test these scalings capture only a narrow range of natural eruptive conditions. In particular, existing analytical scalings are not appropriate for the wind stress conditions typical of the majority of volcanic eruptions. Accordingly, we develop a new analytical scaling for the height of buoyant plumes rising in density-stratified uniform crossflows. We compare this scaling to existing analytical scalings (Morton et al. 1956; Hewett et al. 1971) as well as "functional" scalings (i.e., parameterizations expressed as a function of the Morton et al. (1956) scaling and a regime parameter related to wind stress, Degruyter and Bonadonna (2012), Woodhouse et al. (2013), Carazzo et al. (2014)) using the extensive experimental dataset from Carazzo et al. (2014) along with natural events from a new database including 94 eruptive phases. Our proposed scaling best predicts the height of experimental plumes, which enables us to constrain the ratio of the wind to radial entrainment coefficients. For natural eruptions, the Woodhouse et al. (2013) and Carazzo et al. (2014) scalings, which account explicitly for wind gradient, best predicts plume heights. We show that accounting for atmospheric stratification and wind improves empirical relationships between mass eruption rates and plume heights. For tested scalings, analyze of residual heights for natural eruption supports the hypothesis that volcanic plumes rise higher in a wetter atmosphere. Finally, for analog plumes rising under moderate to high wind stresses, we show that plume shapes evolve over the plume height, violating the self-similarity assumption on which all scalings and integral model results rely. We discuss consequences for relaxing the self-similarity hypothesis as well as potential improvements for standard integral plume models, in turn. (C) 2017 Elsevier B.V. All rights reserved.