Flow Field Characteristics and Lift Changing Mechanism for Half-Rotating Wing in Hovering Flight

Li, Q; Wang, X Y; Han, Qing; Li, C M; Zhi-zhen, Qiu

doi:10.1088/1757-899x/280/1/012022

Cited by 1 publication

(1 citation statement)

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“…38 In previous work, we analyzed the distribution characteristics of vorticity, velocity, and pressure in the flow field of the HRW. 39 The favorable changes in velocity, pressure, and lift are managed through its unique arrangement of vortices, the interactions of which are further analyzed on the basis of vortex characteristics. Here, we further qualitatively analyze how these unique vortices are generated.…”

Section: Computed Flow Field Characteristics Of the Hrwmentioning

confidence: 99%

Aerodynamics of a half-rotating wing in hovering flight: An integrated study

Yuan

Shen

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part G:

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This study introduces a new quasi-flapping wing driving mechanism based on a half-rotating mechanism which is capable of pure rotational flapping rather than the more traditional oscillatory flapping method. Lift models for half-rotating wing (HRW) aircraft in hovering flight are proposed based on the kinematics of a HRW prototype and the flow characteristics near the surface of its wing. Alongside further analytical expressions for lift based on kinematic extractions, computational models and a novel lift validation mechanism are used to reinforce the aerodynamic characteristics of the HRW in hovering flight. The aerodynamics of the HRW are experimentally assessed for different wing layouts and wing materials. Results indicate that the flow field generated by the motion of the wing arranged symmetrically on both sides of the body interfere with each other, causing the average lift coefficient of the paired-wing HRW to be less than that of the single-wing HRW. The average lift coefficient of the flexible wing is larger than that of the rigid wing. In addition, the average lift of the flexible wing increases with increasing flexural compliance within a particular range. Lift forces in different flight conditions are calculated using derived formulas alongside representative computational models, through which the derivation of lift variation for the HRW in hovering flight is validated. The theoretical lift curves show reasonable agreement with numerical simulation results in terms of the time course over one stroke cycle. The mechanisms of the HRW for generation and shedding of vortices in hovering flight are further revealed in computed flow field characteristics results. The velocity vectors of the flow field between the HRW and the symmetrically rotating wing indicate that the HRW with asymmetric rotation can generate lift force effectively. The velocity difference between the wing and the fluid is the key factor influencing the structure of generated vortices. In detailed three-dimensional (3D) vortex flows, our computational fluid dynamics study shows that a horseshoe-shaped vortex is first generated in the early downstroke. The horseshoe-shaped vortex subsequently grows into a doughnut-shaped vortex ring, with a jet stream appearing in its core which forms the downwash. The doughnut-shaped vortex ring eventually elongates into a long arc-shaped wake vortex ring. A large increasing lift force is generated during the upstroke, most likely due to the stable distal attached vortices; and in accordance with this, downwash becomes evident in the vortex ring during the downstroke.

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Section: Computed Flow Field Characteristics Of the Hrwmentioning

confidence: 99%