Spectral proper orthogonal decomposition (SPOD) is a major modal analysis that extracts a dominant structure at each frequency from complicated flow data, such as the wavepacket hidden under turbulent jets. This study investigated the physical interpretation of subdominant multilobe structures in the SPOD modes. A high-speed schlieren movie that exhibited multilobe structures in the SPOD was analyzed using a wavelet-based conditional sampling and averaging (WB-CSA) method. The results of WB-CSA showed spatiotemporally localized wavepackets, which were formed intermittently and convected downstream through growth and decay. Such intermittent convection causes multilobe structures in the SPOD, as illustrated by simple synthetic data that model the results of WB-CSA. Therefore, multilobe structures, together with the most dominant single-lobe wavepackets, can be interpreted as representing the intermittent convection of wavepackets.
Interpretation of Multilobe Wavepackets in Spectral Proper Orthogonal Decomposition of Supersonic Jet
AIAA Journal ; 60 , 1 ; 56-64
2021-08-23
9 pages
Article (Journal)
Electronic Resource
English
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