Abstract
The phase evolution of a separated boundary layer whose separation has been delayed using synthetic jet flow control is presented. Particle Image Velocimetry measurements were made for four control cases corresponding to high and low momentum addition with excitation frequencies targeting the shear-layer and wake instabilities. Coherent structures resulting from this control, their evolution and effect on the wake development are visualized. The excitation frequency of the synthetic jets and the strength of the synthetic jets significantly affect the response of the phase-averaged shear layer, leading to distinct mechanisms of separation delay. Increasing the frequency or the jet strength increases the length of the reattached flow.
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Availability of data and materials
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.
Code availability
The code used for the PIV data processing was OpenPIV, which is a publicly available code hosted on GitHub.
Abbreviations
- AR :
-
Aspect ratio of slot
- \(\alpha\) :
-
Angle of attack
- \(C_\text {B}\) :
-
Blowing ratio
- c :
-
Chord length
- BR :
-
Blockage ratio of airfoil model
- h :
-
Slot width
- d :
-
Slot depth
- \(\delta t\) :
-
Time between images
- \(F^+\) :
-
Reduced frequency
- \(f_\text {e}\) :
-
Excitation frequency
- k :
-
Fluctuating turbulent kinetic energy
- \(\theta\) :
-
Phase angle
- l :
-
Spanwise length of the actuator slot
- \(Re_c\) :
-
Chord-based Reynolds number
- St :
-
Strouhal number
- s :
-
Airfoil span
- \(\tau\) :
-
Period of the excitation
- t :
-
Time
- \(U_\infty\) :
-
Freestream velocity
- \({\mathbf {u}}\) :
-
Velocity vector
- u :
-
Horizontal component of velocity
- v :
-
Vertical component of velocity
- x :
-
The chord-wise coordinate
- y :
-
The normal coordinate
- \({\overline{\cdot }}\) :
-
Time-averaged quantities
- \(\langle \cdot \rangle\) :
-
Phase-averaged quantities
- \({\widetilde{\cdot }}\) :
-
Periodic quantities
- \(\cdot '\) :
-
Fluctuating quantities
- \(|| \cdot ||\) :
-
Magnitude of vector quantities
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Acknowledgements
The authors would like to acknowledge the work of Mark Feero who collected the PIV data at the University of Toronto. In addition, the authors would like to acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), and the University of Toronto Faculty of Applied Science and Engineering through the Dean’s Strategic Fund Award. Computations were performed on the MIST supercomputer at the SciNet HPC Consortium. SciNet is funded by: the Canada Foundation for Innovation, the Government of Ontario; Ontario Research Fund—Research Excellence, and the University of Toronto.
Funding
This work was funded by the University of Toronto Faculty of Applied Science and Engineering’s Dean’s Strategic Fund Award and the Natural Sciences and Engineering Research Council of Canada (NSERC).
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Eric Yang analyzed the data, wrote the first draft and revised the manuscript. Pierre Sullivan and Alis Ekmekci were responsible for funding and revision of the manuscript.
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Yang, E., Ekmekci, A. & Sullivan, P.E. Phase evolution of flow controlled by synthetic jets over NACA 0025 airfoil. J Vis 25, 751–765 (2022). https://doi.org/10.1007/s12650-021-00824-5
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DOI: https://doi.org/10.1007/s12650-021-00824-5