Extracting dominant turbulent structures in supersonic flow using two-dimensional Fourier transform

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

A new image process for quantifying both convection velocities (UC) and scales (λd) of turbulent structures captured in a fast-framing schlieren movie is presented. We obtained 90 time-series schlieren images of a transverse jet into a Mach 2 supersonic flow with 1-MHz sampling. The schlieren images captured not only the shock and expansion waves but also the turbulent structures within the jet and the boundary layer. The image intensities were extracted along the outer edges of the jet and the boundary layer and were remapped as a time–space intensity map. The time–space map exhibited swept stripe patterns, indicating that stable turbulent structures were periodically generated and convected downstream. The angle and interval of the stripe patterns were efficiently extracted using the two-dimensional Fourier transform, which corresponded to UC and λd of the dominant structures. The zero-padding fast Fourier transform and the sub-pixel estimation of the spectral peak positions in the Fourier domain improved the accuracy for evaluating the angle and interval of the stripes, which resulted in the accurate evaluation of UC and λd. The proposed method was validated by comparing UC obtained using the proposed method to those obtained via schlieren image velocimetry for both the transverse jet and the supersonic boundary layer.

Original languageEnglish
Article number98
JournalExperiments in Fluids
Volume58
Issue number8
DOIs
Publication statusPublished - Aug 1 2017

Fingerprint

supersonic flow
Supersonic flow
Fourier transforms
jet boundaries
Boundary layers
boundary layers
supersonic boundary layers
intervals
Fast Fourier transforms
Velocity measurement
Mach number
Time series
elastic waves
Pixels
shock waves
Sampling
convection
pixels
sampling
evaluation

ASJC Scopus subject areas

  • Computational Mechanics
  • Mechanics of Materials
  • Physics and Astronomy(all)
  • Fluid Flow and Transfer Processes

Cite this

Extracting dominant turbulent structures in supersonic flow using two-dimensional Fourier transform. / Kouchi, Toshinori; Masuya, Goro; Yanase, Shinichiro.

In: Experiments in Fluids, Vol. 58, No. 8, 98, 01.08.2017.

Research output: Contribution to journalArticle

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