The energetic motions in turbulent pipe flow
The energetic motions in turbulent pipe flow
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DOI：
10.1063/1.4902436
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发表时间：
2014-12
影响因子：
4.6
通讯作者：
L. Hellström;A. Smits
中科院分区：
文献类型：
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作者：
L. Hellström;A. Smits
用快照和经典的本征正交分解(POD)方法研究了在RED=47000和93000条件下，充分发展的管流中的大尺度高能运动。快照POD模式成对出现，代表相同的方位向模式数，但具有简单的相移。与超大尺度运动(VLSM)相关的前10个快照POD模贡献了平均雷诺切应力的43%，对于前80个模u‘和v’是反相关的，因此它们都对正剪应力事件有贡献。附加运动被包含在低阶模式中，而分离运动直到快照模式数≥15才出现。我们发现快照模式可以引入模混合，而经典模式中避免了这一点。经典的POD也给出了频率信息，证实了低阶模式很好地捕捉到了超大规模运动的行为。
Snapshot and classical proper orthogonal decomposition (POD) are used to examine the large-scale, energetic motions in fully developed turbulent pipe flow at ReD = 47,000 and 93,000. The snapshot POD modes come in pairs, representing the same azimuthal mode number but with a simple phase shift. The first 10 snapshot POD modes, associated with the very large scale motions (VLSMs), contribute 43% of the average Reynolds shear stress, and for first 80 modes u′ and v′ are anti-correlated so that they all contribute to positive shear stress events. The attached motions are contained in the lower order modes, and detached motions do not appear until snapshot POD mode numbers ≥15. We find that snapshot POD can introduce mode mixing, which is avoided in classical POD. Classical POD also gives frequency information, confirming that the low order modes capture well the behavior of the very large scale motions.