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Passive Bio-Inspired Flow Control: T...

Othman, Ahmed Khaled,

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Passive Bio-Inspired Flow Control: The FSI of Covert-Inspired Flaps in 2D & 3D Flows /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Passive Bio-Inspired Flow Control: The FSI of Covert-Inspired Flaps in 2D & 3D Flows // Ahmed Khaled Othman.
作者:	Othman, Ahmed Khaled,
面頁冊數:	1 electronic resource (136 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
Contained By:	Dissertations Abstracts International86-12B.
標題:	Mechanical engineering. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32002205
ISBN:	9798280748002

Passive Bio-Inspired Flow Control: The FSI of Covert-Inspired Flaps in 2D & 3D Flows /
Othman, Ahmed Khaled,

Passive Bio-Inspired Flow Control: The FSI of Covert-Inspired Flaps in 2D & 3D Flows /Ahmed Khaled Othman. - 1 electronic resource (136 pages)

Source: Dissertations Abstracts International, Volume: 86-12, Section: B.

Bioinspired flow control strategies offer a new approach to enhance the efficiency and adaptability of small-scale uncrewed aerial vehicles (SUAVs), which remain far less agile than their biological counterparts, birds. One of the flow control strategies birds implement is the deployment of their covert feathers. This dissertation provides a physics-based understanding of covert-inspired flow control devices in two-dimensional (2D) and three-dimensional (3D) flows at a Reynolds number relevant to both birds and SUAVs (Re = 200,000).First, the covert-inspired flaps are shown to effectively mitigate flow separation post stall, with up to 22% lift improvement and 7% drag reduction in the 2D study. The flap's inertia and hinge stiffness tune its mean deflection angle and oscillations to enhance the flow control mechanism employed by the flaps. Trailing-edge (TE) flaps act as pressure dams, with maximum effectiveness when the flap is normal to the airfoil, while leading-edge (LE) flaps interact with the shear layer to reduce the adverse pressure gradient, performing best when this interaction is stable with minimal oscillations. Second, an analytical model shows that TE flaps oscillate at their natural frequency due to low local flow velocities at this flap location, whereas LE flaps experience higher oscillation frequencies due to added aerodynamic stiffness induced by higher local flow velocities.The remainder of the dissertation investigates the impact of flow three-dimensionality on covert-inspired flaps. Results indicate the robustness of the LE flap to 3D effects, as it passively adapts to the shear layer height, maintaining lift benefits across wings with different aspect ratios. In contrast, the TE flap is highly sensitive to the flow three-dimensionality, being more effective when the wake size is comparable to the flap length. Finally, a design framework for span-distributed flaps on an aspect ratio AR = 4 wing reveals that inboard LE flaps exhibit a constructive additive effect, while a single mid-span TE flap provides the most aerodynamic benefits. Moreover, the simultaneous deployment of the best-performing LE and TE configurations leads to superior lift benefits, demonstrating the potential of exploiting both the shear-layer interaction and the pressure dam effect in 3D flows.

English

ISBN: 9798280748002Subjects--Topical Terms:

649730
Mechanical engineering.
Subjects--Index Terms:

Aerodynamics

Passive Bio-Inspired Flow Control: The FSI of Covert-Inspired Flaps in 2D & 3D Flows /
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520 $a Bioinspired flow control strategies offer a new approach to enhance the efficiency and adaptability of small-scale uncrewed aerial vehicles (SUAVs), which remain far less agile than their biological counterparts, birds. One of the flow control strategies birds implement is the deployment of their covert feathers. This dissertation provides a physics-based understanding of covert-inspired flow control devices in two-dimensional (2D) and three-dimensional (3D) flows at a Reynolds number relevant to both birds and SUAVs (Re = 200,000).First, the covert-inspired flaps are shown to effectively mitigate flow separation post stall, with up to 22% lift improvement and 7% drag reduction in the 2D study. The flap's inertia and hinge stiffness tune its mean deflection angle and oscillations to enhance the flow control mechanism employed by the flaps. Trailing-edge (TE) flaps act as pressure dams, with maximum effectiveness when the flap is normal to the airfoil, while leading-edge (LE) flaps interact with the shear layer to reduce the adverse pressure gradient, performing best when this interaction is stable with minimal oscillations. Second, an analytical model shows that TE flaps oscillate at their natural frequency due to low local flow velocities at this flap location, whereas LE flaps experience higher oscillation frequencies due to added aerodynamic stiffness induced by higher local flow velocities.The remainder of the dissertation investigates the impact of flow three-dimensionality on covert-inspired flaps. Results indicate the robustness of the LE flap to 3D effects, as it passively adapts to the shear layer height, maintaining lift benefits across wings with different aspect ratios. In contrast, the TE flap is highly sensitive to the flow three-dimensionality, being more effective when the wake size is comparable to the flap length. Finally, a design framework for span-distributed flaps on an aspect ratio AR = 4 wing reveals that inboard LE flaps exhibit a constructive additive effect, while a single mid-span TE flap provides the most aerodynamic benefits. Moreover, the simultaneous deployment of the best-performing LE and TE configurations leads to superior lift benefits, demonstrating the potential of exploiting both the shear-layer interaction and the pressure dam effect in 3D flows.
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