Experiments on turbulent metal-silicate mixing in a magma ocean
Experiments on turbulent metal-silicate mixing in a magma ocean
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DOI：
10.1016/j.epsl.2011.08.041
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发表时间：
2011-10-15
影响因子：
5.3
通讯作者：
Cardin, Philippe
中科院分区：
文献类型：
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作者：
Deguen, Renaud;Olson, Peter;Cardin, Philippe
我们将实验室流体动力学实验的结果与两相浮力羽流和热气流中湍流夹带的理论模型进行比较，以估计星子或行星胚胎的铁芯与岩浆池中熔融硅酸盐之间的混合量，该岩浆池是在吸积过程中与生长中的行星撞击而形成的。我们通过实验证明，不混溶流体中的湍流羽流碎裂成液滴，并且在相同的动力学条件下，液滴分布的包络线与单相流体中的湍流羽流的包络线无法区分，这意味着湍流夹带概念适用于不混溶流体的混合。对两相湍流热流的时间演化进行了一系列实验，代表着一个星子核心，在球形流体中受到自身负浮力的影响，代表着一个撞击产生的岩浆池。在这些实验中观察到两个阶段的混合：第一个阶段对应于热气流自由落体期间的湍流夹带，第二个阶段对应于热气流到达岩浆池底部后形成的湍流重力流中的夹带。我们证明，岩浆池中金属和硅酸盐液体之间的混合量取决于金属碎片的劳斯数，并随着原行星的半径而迅速增加。我们推导出球形岩浆池中金属硅酸盐混合的相似模型，假设湍流液态金属相的夹带系数恒定。该模型支持我们的实验发现，即撞击器的小金属核心将在深层岩浆池中被稀释（即混合），但大型撞击核心在到达岩浆池底部之前不会完全稀释。 (C) 2011 Elsevier B.V. 保留所有权利。
We compare the results of laboratory fluid dynamics experiments with theoretical models of turbulent entrainment in two-phase buoyant plumes and thermals to estimate the amount of mixing between the iron core of a planetesimal or planetary embryo and the molten silicates in a magma pool formed by its impact with a growing planet during accretion. We demonstrate experimentally that turbulent plumes in immiscible fluids fragment into droplets, and that the envelope of the droplet distribution is indistinguishable from the envelope of a turbulent plume in a single phase fluid under the same dynamical conditions, implying that turbulent entrainment concepts are applicable to immiscible fluids mixing. A series of experiments are made on the time evolution of a two-phase turbulent thermal, representing a planetesimal core, falling under its own negative buoyancy in a spherical fluid, representing an impact-produced magma pool. Two stages of mixing are observed in these experiments: the first corresponding to turbulent entrainment during free-fall of the thermal, the second corresponding to entrainment in turbulent gravity currents that form after the thermal reaches the base of the magma pool. We demonstrate that the amount of mixing between metals and silicate liquids in a magma pool depends on the Rouse number of the metal fragments and increases rapidly with the radius of the proto-planet. We derive a similarity model for metal-silicate mixing in a spherical magma pool, assuming a constant entrainment coefficient for the turbulent liquid metal phase. This model supports our experimental finding that a small metal core of an impactor will become diluted (i.e., mix) within a deep magma pool, but a large impacting core will not fully dilute before reaching the base of the magma pool. (C) 2011 Elsevier B.V. All rights reserved.