Short-time proper orthogonal decomposition of time-resolved schlieren images for transient jet screech characterization

Lim, H. D.Nanyang Technol Univ, Sch Mech & Aerosp Engn, 50 Nanyang Ave, Singapore 639798, Singapore. (författare)

QC 20210127
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 degrees bevelled jets, while none was detected for the 60 degrees 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.

Wei, X. F.Nanyang Technol Univ, Sch Mech & Aerosp Engn, 50 Nanyang Ave, Singapore 639798, Singapore. (författare)
Zang, B.Nanyang Technol Univ, Sch Mech & Aerosp Engn, 50 Nanyang Ave, Singapore 639798, Singapore.;Univ Bristol, Dept Aerosp Engn, Queens Bldg,Univ Walk, Bristol BS8 1TR, Avon, England. (författare)
Vevek, U. S.Nanyang Technol Univ, Sch Mech & Aerosp Engn, 50 Nanyang Ave, Singapore 639798, Singapore. (författare)
Mariani, Raffaello,Assistant Prof.1981-Nanyang Technol Univ, Sch Mech & Aerosp Engn, 50 Nanyang Ave, Singapore 639798, Singapore(Swepub:kth)u18c6alu (författare)
New, T. H.Nanyang Technol Univ, Sch Mech & Aerosp Engn, 50 Nanyang Ave, Singapore 639798, Singapore. (författare)
Cui, Y. D.Natl Univ Singapore, Temasek Labs, 5A Engn Dr 1, Singapore 117411, Singapore. (författare)
Nanyang Technol Univ, Sch Mech & Aerosp Engn, 50 Nanyang Ave, Singapore 639798, Singapore.Nanyang Technol Univ, Sch Mech & Aerosp Engn, 50 Nanyang Ave, Singapore 639798, Singapore.;Univ Bristol, Dept Aerosp Engn, Queens Bldg,Univ Walk, Bristol BS8 1TR, Avon, England. (creator_code:org_t)

Av författaren/redakt...: Lim, H. D.; Wei, X. F.; Zang, B.; Vevek, U. S.; Mariani, Raffael ...; New, T. H.; visa fler...; Cui, Y. D.; visa färre...

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