Addressing complexity in laboratory experiments: the scaling of dilute multiphase flows in magmatic systems
Addressing complexity in laboratory experiments: the scaling of dilute multiphase flows in magmatic systems
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DOI：
10.1016/j.jvolgeores.2004.11.001
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发表时间：
2005-03-15
影响因子：
2.9
通讯作者：
Breidenthal, RE
中科院分区：
文献类型：
--
作者：
Burgisser, A;Bergantz, GW;Breidenthal, RE
岩浆体系中稀薄多相混合物的运动学和动力学标度是实验室实验地质逼真的唯一保证。我们提出的标度关系可以提供一个更完整的框架来刻度稀释的岩浆系统，因为它们明确地考虑了颗粒(晶体、气泡或火山碎屑)和连续相(液体或气体)之间反馈所引起的复杂性。我们考虑了三个典型的火成岩系统：岩浆室、火山羽流和火山碎屑流，并为已发表的关于这些系统的实验提供了拟议的标度关系的估计。稀薄的岩浆混合物可以表现出一系列不同的动力机制，我们用平均(欧拉)性质和瞬时(拉格朗日)变量的组合来表征这些动力机制。混合物的欧拉性质产生雷诺数(Re)，它表示连续相中的不稳定程度。颗粒的拉格朗日加速度是粘性阻力和重力的函数，并由这两种力导出了斯托克斯数(S-T)和稳定数(Sigma(T))，这两个无量纲数描述了混合物中颗粒的动力学行为。对17项与火山碎屑涌流和火山柱有关的实验研究的汇编表明，有必要在混合转变(Re>；10(4))以上进行实验，并对S-T和西格玛(T)进行刻度。在涌流和羽流中存在的粒子动力学机制中，有些值得特别关注，例如中尺度结构对输送和沉积过程的作用，或向湍流过渡对粒子聚集和扩散的影响。7项与岩浆体有关的实验研究表明，在层流状态下，晶体主要跟随熔体的运动，因此体系的物理状态可以近似为单相。在向湍流过渡的过程中，岩浆可能具有层流区和重要的速度梯度的空间不均匀分布。这种不均一性对晶体分选具有很大的潜力。总之，Re-S-T-Sigma(T)框架表明，尽管对与岩浆系统有关的过程进行了大量的实验研究，但仍有一些可能是最重要的地质参数范围需要在实验室规模上解决。(C)2004爱思唯尔B.V.保留所有权利。
The kinematic and dynamic scaling of dilute multiphase mixtures in magmatic systems is the only guarantee for the geological verisimilitude of laboratory experiments. We present scaling relations that can provide a more complete framework to scale dilute magmatic systems because they explicitly take into account the complexity caused by the feedback between particles (crystal, bubble, or pyroclast) and the continuous phase (liquid or gas). We consider three canonical igneous systems: magma chambers, volcanic plumes, and pyroclastic surges, and we provide estimates of the proposed scaling relations for published experiments on those systems. Dilute magmatic mixtures can display a range of distinct dynamical regimes that we characterize with a combination of average (Eulerian) properties and instantaneous (Lagrangian) variables. The Eulerian properties of the mixtures yield the Reynolds number (Re), which indicates the level of unsteadiness in the continuous phase. The Lagrangian acceleration of particles is a function of the viscous drag and gravity forces, and from these two forces are derived the Stokes number (S-T) and the stability number (Sigma(T)), two dimensionless numbers that describe the dynamic behavior of the particles within the mixture. The compilation of 17 experimental studies relevant for pyroclastic surges and volcanic ;plumes indicates that there is a need for experiments above the mixing transition (Re > 10(4)) and for scaling S-T and Sigma(T). Among the particle dynamic regimes present in surges and plumes, some deserve special attention, such as the role of mesoscale structures on transport and sedimentary processes or the consequences of the transition to turbulence on particle gathering and dispersal. The compilation of seven experimental studies relevant to magma bodies indicates that, in the laminar regime, crystals mostly follow the motion of the melt, and thus the physical state of the system can be approximated as single phase. In the transition to turbulence, magmas can feature spatially heterogeneous distributions of laminar regions and important velocity gradients. This heterogeneity has a strong potential for crystals sorting. In conclusion, the Re-S-T-Sigma(T) framework demonstrates that, despite numerous experimental studies on processes relevant to magmatic systems, some and perhaps most geologically important parameter ranges still need to be addressed at the laboratory scale. (c) 2004 Elsevier B.V. All rights reserved.