Mechanism of unconventional aerodynamic characteristics of an elliptic airfoil

Sun, Wei; Gao, Zhenghong; Du, Yajie; Xu, Fang

doi:10.1016/j.cja.2015.03.009

Cited by 16 publications

(6 citation statements)

References 18 publications

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“…Counter-rotating vortices were also observed by Poelma [19] in their study using a dynamically-scaled wing in mineral oil at Re of 256. In the numerical study at higher Reynolds numbers of 10 4 to 10 6 done by Wei et al, [20] vortex dipoles were also seen in the flow visualization.…”

Section: Introductionmentioning

confidence: 75%

The Drag of an Elliptical Airfoil at a Reynolds Number of 1000

Tobing

2022

CFDL

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There have been many studies on the mechanisms of unsteady aerodynamics, such as leading-edge vortex (LEV) formation, wing-wake interaction, and spanwise flow. Spanwise flow can only be observed on three-dimensional wing models; however other phenomena such as LEV and wing-wake interaction can be captured using two-dimensional airfoil models. This study focuses on two-dimensional elliptical airfoil because this profile can generate counter-rotating vortices used by insects to generate aerodynamic forces. This research aims to analyze the drag production of two-dimensional elliptical airfoils flapping with bumblebee-inspired kinematics in asymmetrical normal-hovering mode at a typical Reynolds number range of . It is found that drag is generated during the downstroke while thrust during the upstroke. It is also found that the creation and shedding of counter-rotating vortices are closely related to the generation of thrust. The results also indicate that asymmetrical strokes can be used in normal hovering to minimize drag or produce thrust.

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Section: Introductionmentioning

confidence: 75%

The Drag of an Elliptical Airfoil at a Reynolds Number of 1000

Tobing

2022

CFDL

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“…The collective pitch of main rotor decreases to zero at the end of the transition process. As the CRW adopts symmetric aerofoils [7], [14], the main rotor produces no lift now, and the lift is completely provided by the canard wing and horizontal tail. The power of the main rotor can be cut off now and the main rotor will gradually speed down.…”

Section: A Transition Scheme Of the Crw Aircraftmentioning

confidence: 99%

“…He et al [5] and Deng et al [6] studied the aerodynamic interference between the main rotor and fixed wings based on wind tunnel tests. Sun et al [7], [8] explored the aerodynamic characteristics of the aerofoil of main rotor using computational fluid dynamics (CFD). Pandya and Aftosmis [9] investigated the aerodynamic load change of CRW via non-viscous numerical simulation during transition from helicopter to fixed-wing mode.…”

Section: Introductionmentioning

confidence: 99%

“…The aerodynamic interactions among components are hard to acquire by mechanism analysis. CFD [7], [8] is employed to obtain the aerodynamic forces and moments of the canard wing, horizontal tail, vertical tail and fuselage under the downwash of the main rotor. The flight dynamics model of the CRW aircraft in transition mode is established based on the above results.…”

Section: Introductionmentioning

confidence: 99%

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Trim Strategy, Control Model, and Flight Dynamics Characteristics of Canard Rotor/Wing Aircraft in Transition Mode

Gao

Yang

et al. 2019

IEEE Access

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The transition mode of canard rotor/wing (CRW) aircraft is complex and important. During the transition flight, components that generate lift are transferred from one to another, in addition, the redundancy of control system may induce control conflict even plane crash if they don't cooperate well. It is significant to investigate the trim strategy, redundant control, and flight dynamics characteristics of CRW during transition flight. First, aerodynamic forces and moments were calculated by combining the blade element theory, computational fluid dynamics (CFD) and engineering estimation, and the motion equations of CRW in transition mode are established. Next, by analyzing the principle of transition flight, a trim strategy is proposed, and the trim results are credible and reasonable. Then, a control model for solving redundant control is proposed, which can realize simple and effective control during the transition process. Finally, by analyzing the eigenvalues, it is found that the stability of most modes grows with the increase of forwarding flying speed in the transition process, whereas the variation of minority modes is complicated. The results demonstrate the complexity of dynamic characteristics of CRW in transition mode. The trim strategy and control model and the analysis of the dynamic characteristics in the paper can be used for the subsequent control system design and overall optimization design. INDEX TERMS Canard rotor/wing aircraft, transition scheme, model building, flight dynamics, control allocation, dynamics analysis.

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“…Poelma et al [22] studied a dynamically-scaled wing moving in mineral oil and observed a pair of counter-rotating structures (Re = ). Wei, et al [23] numerically studied elliptical airfoils at Reynolds numbers ranging from 10 4 to 10 6 and they also captured vortex dipoles in the flow visualization. The current work extends these published works by implementing the kinematics of bumblebees on the elliptical airfoil.…”

Section: Introductionmentioning

confidence: 99%

Lift Generation of an Elliptical Airfoil at a Reynolds Number of 1000

Tobing

2019

IJAME

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Bumblebees cannot fly! That conclusion is likely to be drawn by scientists who analysed the insect using aerodynamics of stationary wings such as that of a passenger aircraft. Looking at the insect again using a newfound understanding of unsteady aerodynamics; it is clear why bumblebees can fly. Bumblebees utilise mechanisms behind unsteady aerodynamics such as leading-edge vortices (LEVs) formation, wake capture, and rapid end-of-stroke rotation to generate forces that enable the insect to fly. This study focuses on two-dimensional (2D) elliptical airfoil. Earlier works found the aerodynamic characteristics of an elliptical airfoil to differ greatly from a conventional airfoil, and that this airfoil shape could generate the counter-rotating vortices used by insects to generate lift. Therefore, this research aims to study the lift generation of a bumblebee-inspired elliptical airfoil in a normal hovering flight. This study focuses on hovering flight with the insect flies in a nearly stationary position, which explains the importance of lift generation to stay aloft. The motion of the elliptical airfoil is inspired by the flapping kinematics of bumblebees at a typical Reynolds number range of . It is found that the current two-dimensional model is capable of capturing the counter-rotating vortices and correlates the formation of these structures to a high production of lift. These results show that bumblebees utilise these counter-rotating vortices to generate lift enough to fly in hovering flight. This results also indicate that flapping 2D elliptical airfoils can be used to investigate their 3D wing counterparts, which translate to a reduced time and computing costs.

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Mechanism of unconventional aerodynamic characteristics of an elliptic airfoil

Cited by 16 publications

References 18 publications

The Drag of an Elliptical Airfoil at a Reynolds Number of 1000

The Drag of an Elliptical Airfoil at a Reynolds Number of 1000

Trim Strategy, Control Model, and Flight Dynamics Characteristics of Canard Rotor/Wing Aircraft in Transition Mode

Lift Generation of an Elliptical Airfoil at a Reynolds Number of 1000

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