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Covert feathers are a set of self-actuating, passively deployable feathers located on the upper surfaces of wings that augment lift at post-stall angles of attack. Due to these benefits, the study of covert-inspired passive flow control devices is becoming an increasingly active area of research. In this work, we numerically investigate the aerodynamic benefits of torsionally mounting five covert-inspired flaps on the upper surface of a NACA0012 airfoil. Two-dimensional high-fidelity simulations of the flow past the airfoil–flap system at low Re=1000 and a high angle of attack of 20∘ were performed. A parametric study was conducted by varying the flap moment of inertia and torsional hinge stiffness to characterize the aerodynamic performance of this system. Lift improvements as high as 25% were attained. Two regimes of flap dynamics were identified that provided considerable aerodynamic benefits. A detailed investigation of the flow physics of both these regimes was conducted to understand the physical mechanisms by which the passively deployed flaps augmented the lift of the airfoil. In both regimes, the flap was found to act as a barrier in preventing the upstream propagation of reverse flow due to flow separation and trailing edge vortex. The torsional spring and flap inertia yielded additional flap dynamics that further modulated the surrounding flow and associated performance metrics. We discuss some of these fluid–structure interaction effects in this article.
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Passive flow control for the E423 airfoil utilizing an equilateral triangular trip
A passive flow control technique of utilizing an equilateral triangular trip close to the leading edge was developed and tested for a micro-scale Eppler E423 airfoil at a Reynolds number based on the chord of 40 000. The analysis was carried out via high-order wall-resolved large eddy simulation using the computational solver HpMusic. Angles of attack of 5° and 20° were tested. It was shown that at an angle of attack of 5°, the trip height of two times the local boundary layer thickness outperformed existing passive flow control techniques from the literature by almost a factor of five in terms of the lift-to-drag ratio. To understand the underlying physics which allowed the trip to provide this very significant performance benefit, metrics such as pressure coefficient profiles, oil flows, iso-surfaces of Q-criteria, and leading-edge flow behavior were examined. It was found that this trip configuration simultaneously removed the flow separation regions on both the suction and pressure sides of the wing.
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- Award ID(s):
- 2117449
- PAR ID:
- 10569858
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Physics of Fluids
- Volume:
- 35
- Issue:
- 12
- ISSN:
- 1070-6631
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0174284
