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Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods
Published on: April 23, 2018
Analysis of the transitional flow field over a fixed hummingbird wing
Yossef Elimelech1, Charles P Ellington
1University of Cambridge, Department of Zoology, Downing Street, Cambridge CB2 3EJ, UK. yosie@aerodyne.technion.ac.il
The Journal of Experimental Biology
|September 22, 2012
Summary
This study reveals how airflow transitions from smooth to turbulent over a hummingbird wing model. Higher Reynolds numbers (15,000) promote flow reattachment, crucial for understanding bird flight aerodynamics.
Area of Science:
- Fluid dynamics
- Aerodynamics
- Bio-inspired engineering
Background:
- Understanding the complex airflow over flapping wings is key to bio-inspired flight.
- Hummingbird wings operate at low Reynolds numbers, presenting unique aerodynamic challenges.
Purpose of the Study:
- To analyze the laminar-to-turbulent transition of airflow over a stationary hummingbird wing model.
- To investigate flow separation and disturbance amplification at varying Reynolds numbers.
Main Methods:
- Utilized constant-temperature anemometry and stereo particle image velocimetry for high-fidelity flow field analysis.
- Examined flow characteristics at chord-based Reynolds numbers from 5,000 to 15,000.
Main Results:
- Observed a distinct laminar-to-turbulent transition process over the wing model.
- At non-zero angles of attack, flow separation and shear layer formation were evident.
- Unsteady flow disturbances amplified significantly at Reynolds numbers as low as 5,000.
Conclusions:
- Flow reattachment due to disturbance growth was only sufficient at a Reynolds number of 15,000.
- Flow disturbances with a Strouhal number of unity and above were found to be three-dimensional at Re=5,000.
- This research provides foundational insights into the aerodynamics of flapping wings in the studied Reynolds number regime.
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