Determination of mixing time and degree of homogeneity in stirred vessels with large eddy simulation
Determination of mixing time and degree of homogeneity in stirred vessels with large eddy simulation
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DOI：
10.1016/j.ces.2004.10.048
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发表时间：
2005-04
影响因子：
4.7
通讯作者：
S. L. Yeoh;G. Papadakis;M. Yianneskis
中科院分区：
文献类型：
--
作者：
S. L. Yeoh;G. Papadakis;M. Yianneskis
虽然反应混合是最感兴趣的大多数工业混合敏感的过程中，被动标量行为和混合的透彻理解提供了一个重要的一步，在理解相关的过程中，特别是当湍流条件下，目前在大部分的容器体积。本文采用大涡模拟技术对Rushton桨搅拌容器中惰性标量的混合进行了数值模拟。最近的研究表明，这种方法的能力，在搅拌容器中的湍流场的准确建模。然而，据作者所知，迄今为止还没有对混合特性进行全面研究，并根据实验数据对混合时间进行评估。目前的模拟提供了一个非常详细的图片的标量浓度的空间和时间的演变，不能得到与标准的Alfred的平均Navier-Stokes方法。最大的标量波动被检测到的注射平面中，在该区域靠近叶轮的湍流水平是最高的。标量浓度记录在其他几个点内的域揭示了不同的混合模式在整个容器。预测的混合时间比较好，平均在18%以内，与文献中报道的相关性确定的值。该协议证明了这种建模方法的能力，准确地模拟搅拌容器中的混合特性，因此可用于工业容器设计的优化。
Although reactive mixing is of utmost interest for most industrial mixing-sensitive processes, a thorough understanding of passive scalar behaviour and mixing provides an important step in understanding of the relevant processes, especially when turbulent flow conditions are present over much of the vessel volume. The objective of the present work is to characterise the mixing of an inert scalar in a vessel stirred by a Rushton impeller using the large eddy simulation technique. Recent studies have demonstrated the capability of this approach for the accurate modelling of the turbulent flow field in a stirred vessel. However, to the best of the authors’ knowledge, no comprehensive investigation of mixing characteristics and assessment of mixing time against experimental data has been performed so far. The current simulations provides a very detailed picture of the spatial and temporal evolution of the scalar concentration that cannot be obtained with the standard Reynold's averaged Navier–Stokes approach. The largest scalar fluctuations were detected in the injection plane, in the area close to the impeller where turbulence levels are highest. Scalar concentrations recorded at several other points inside the domain revealed different mixing patterns across the vessel. The predicted mixing time compared well, on average within 18%, with values determined from correlations reported in the literature. This agreement demonstrates the capability of this modelling approach to simulate accurately the mixing characteristics in a stirred vessel and therefore to be employed for the optimisation of industrial vessel designs.