Application of Proper Orthogonal Decomposition to the morphological analysis of confined co-axial jets of immiscible liquids with comparable densities
Application of Proper Orthogonal Decomposition to the morphological analysis of confined co-axial jets of immiscible liquids with comparable densities
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DOI：
10.1063/1.4900944
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发表时间：
2014-11
影响因子：
4.6
通讯作者：
G. Charalampous;Y. Hardalupas
中科院分区：
文献类型：
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作者：
G. Charalampous;Y. Hardalupas
在喷嘴出口附近，研究了密度相当的不混溶液体（中心与环形流密度比为8：10）的受限同轴流的影响下圆形液体射流的发展。考虑了两种流动状态;一种是环形流比中心射流快，因此中心液体射流加速，另一种是环形流较慢，因此中心液体射流减速。中央喷流是通过高速摄影显现出来的。根据中心射流的雷诺数Re（在525 < Re < 2725范围内）、韦伯数We的修改定义（允许区分加速流和减速流，在−22 < We < 67范围内）和环形与中心动量比MR，确定并分类了射流发展的三种模式。在3.6 < MR < 91的范围内。通过使用本征正交分解（POD）处理时间分辨射流图像，可以将射流形态的描述减少到少量的空间模式，这隔离了射流发展的最显著形态。通过这种方式，可以清楚地识别界面上不稳定性的时间和空间特征，这突出了POD相对于直接观察图像的优势。建立了流动参数与界面波之间的关系。的界面不稳定性的波长被发现依赖于最快的移动流的速度，这是相反的发现具有较大的密度差的流体。
The development of a round liquid jet under the influence of a confined coaxial flow of an immiscible liquid of comparable density (central to annular flow density ratio of 8:10) was investigated in the vicinity of the nozzle exit. Two flow regimes were considered; one where the annular flow is faster than the central jet, so the central liquid jet is accelerated and one where the annular flow is slower, so the central liquid jet is decelerated. The central jet was visualised by high speed photography. Three modes of jet development were identified and classified in terms of the Reynolds number, Re, of the central jet which was in the range of 525 < Re < 2725, a modified definition of the Weber number, We, which allows the distinction between accelerating and deceleration flows and was in the range of −22 < We < 67 and the annular to central Momentum Ratio, MR, of the two streams which was in the range of 3.6 < MR < 91. By processing the time resolved jet images using Proper Orthogonal Decomposition (POD), it was possible to reduce the description of jet morphology to a small number of spatial modes, which isolated the most significant morphologies of the jet development. In this way, the temporal and spatial characteristics of the instabilities on the interface were clearly identified which highlights the advantages of POD over direct observation of the images. Relationships between the flow parameters and the interfacial waves were established. The wavelength of the interfacial instability was found to depend on the velocity of the fastest moving stream, which is contrary to findings for fluids with large density differences.