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Investigation of time-frequency analysis and transitional boundary layer over a pitching airfoil

Akhlaghi, H ; Sharif University of Technology | 2021

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  1. Type of Document: Article
  2. DOI: 10.24200/SCI.2020.53393.3218
  3. Publisher: Sharif University of Technology , 2021
  4. Abstract:
  5. Transitional boundary layer over a pitching airfoil at low Reynolds number (Re = 2:7 × 105) is experimentally investigated using space-frequency and time-frequency analyses of hot- film signals. Boundary layer events are visualized based on the space-frequency and time-frequency plots. The precursor phenomenon for turbulent and fully separated flows is presented based on the time-frequency analysis. A new technique based on time-frequency analysis of hot- film signals is introduced to measure the transition onset and relaminarization locations. This technique functions based on the analysis of high-frequency disturbances of the measured data. Significant attention has been drawn to the spatial/temporal progression of the transition onset and relaminarization points rather than to the static values for different oscillation frequencies and amplitudes. Investigations are performed prior to, within, and beyond the static stall angle of attack conditions. The results obtained from this new technique are discussed and compared with the observations of previous investigators. © 2021 Sharif University of Technology. All rights reserved
  6. Keywords:
  7. Airfoils ; Angle of attack ; High frequency disturbance ; Low Reynolds number ; Oscillation frequency ; Pitching airfoils ; Precursor phenomena ; Space frequency ; Time frequency analysis ; Transitional boundary layers ; Boundary layers ; boundary layer ; detection method ; experimental study ; oscillation ; performance assessment ; Reynolds number
  8. Source: Scientia Iranica ; Volume 28, Issue 2 B , 2021 , Pages 860-876 ; 10263098 (ISSN)
  9. URL: http://scientiairanica.sharif.edu/article_21816.html