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Title: Short-time proper orthogonal decomposition of time-resolved schlieren images for transient jet screech characterization
Authors: Lim, Desmond Haoxiang
Wei, Xiaofeng
Zang, Bin
Vevek, U. S.
Mariani, Raffaello
New, Tze How
Cui, Y. D.
Keywords: Engineering::Mechanical engineering
Issue Date: 2020
Source: Lim, D. H., Wei, X., Zang, B., Vevek, U. S., Mariani, R., New, T. H. & Cui, Y. D. (2020). Short-time proper orthogonal decomposition of time-resolved schlieren images for transient jet screech characterization. Aerospace Science and Technology, 107, 106276-.
Project: MOE2014-T2-1-002 
Journal: Aerospace Science and Technology 
Abstract: Short-time Proper Orthogonal Decomposition (POD) is proposed as an image-based technique to study the transient jet screech characteristics of moderately under-expanded supersonic jets emanating from a circular baseline and two bevelled nozzles. Time-resolved schlieren imaging of turbulent flow structures were performed with an ultrahigh-speed schlieren setup. Short-time POD was performed by systematically sampling image-series with a short time delay, performing PODs and applying spectral analyses on the first POD mode coefficients, and plotting the peak frequencies from the resulting PSDs into a peak frequency-occurrence count histogram. The results are in good agreement with the near-field noise spectra and wavelet transform analysis of the microphone measurements, which revealed intermittent jet screech occurrences at St=0.25 for both baseline and 30° bevelled jets, while none was detected for the 60° bevelled jet. In particular, the occurrence counts of the frequency bins is proposed as a suitable parameter to characterize the intermittent nature of jet screech, with the frequency bin revealing the jet screech frequency if present. The present study demonstrates the advantage of short-time POD analysis on time-resolved schlieren images over traditional image-based POD methods, which includes computational gains from parallelization, the ability to handle much larger datasets and revealing insights into a transient flow and noise phenomenon.
ISSN: 1270-9638
DOI: 10.1016/j.ast.2020.106276
Schools: School of Mechanical and Aerospace Engineering 
Rights: © 2020 Elsevier Masson SAS. All rights reserved.
Fulltext Permission: none
Fulltext Availability: No Fulltext
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