The present study aims to identify the dominant coherent structures in the wall jet flow subjected to external pulsation at Reynolds number 2600 (based on average jet exit velocity and nozzle diameter). The forcing frequency is varied between St = 0 and 0.99 (St is the Strouhal number). Quadrant analysis is employed to identify the relative contribution of different quadrant motions to the total Reynolds shear stress. Unlike boundary layer flows and channel flows, two distinct regions (inner shear region and outer shear region) are observed in the wall jet flows, and the characteristics of different quadrant motions change in these regions. About 70% of the total shear stress is contributed from the first and fourth quadrants in the outer shear region. We observe that ejection motion is more energetic than sweep motion in the downstream direction, although less frequent. The ejection motion is observed to be more violent for St = 0.44 than for the other frequencies. A proper orthogonal decomposition (POD) analysis reveals while the modal structures exist in different regions of the wall for different jet pulsation; there are no dominant modes (30 modes are required to recover about 75% of the total energy), and the energy is fairly distributed over a large number of modes. However, the POD analyses are capable of capturing the response of the wall jet to different jet pulsations. The most dominant and strongest modal structures are found nearer to the impingement region of the wall when St = 0.44 and the jet tends to laminarize for St > 0.9.
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September 2021
Research Article|
September 01 2021
Dynamics of wall jet flow under external pulsation
Abhishek Mishra
;
Abhishek Mishra
1
Department of Mechanical Engineering, Indian Institute of Technology Bombay
, Powai, Mumbai 400076, India
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Lyazid Djenidi
;
Lyazid Djenidi
2
School of Engineering, University of Newcastle
, Callaghan, NSW 2308, Australia
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Amit Agrawal
Amit Agrawal
a)
1
Department of Mechanical Engineering, Indian Institute of Technology Bombay
, Powai, Mumbai 400076, India
a)Author to whom correspondence should be addressed: amit.agrawal@iitb.ac.in
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a)Author to whom correspondence should be addressed: amit.agrawal@iitb.ac.in
Physics of Fluids 33, 095103 (2021)
Article history
Received:
May 24 2021
Accepted:
August 12 2021
Citation
Abhishek Mishra, Lyazid Djenidi, Amit Agrawal; Dynamics of wall jet flow under external pulsation. Physics of Fluids 1 September 2021; 33 (9): 095103. https://doi.org/10.1063/5.0057695
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