• Bionic wing flaps improve wind energy ef

    From ScienceDaily@1:317/3 to All on Tue Mar 22 22:30:46 2022
    Bionic wing flaps improve wind energy efficiency
    Combining engineered flaps with other structures inspired by seagull
    wings improves lift, reduces stalling in wind energy turbine blades

    Date:
    March 22, 2022
    Source:
    American Institute of Physics
    Summary:
    Scientists show a bionic approach combining features of a seagull's
    wing with an engineered flow control accessory, known as a Gurney
    flap, can greatly improve wind turbine performance. To achieve the
    best aerodynamic performance, the scientists simulated the use of
    the combined flow control accessory in a variety of situations,
    including high and low angle of attack and pre- and post-stall
    scenarios. They compared their computational simulations to
    experimental results for an aircraft wing undergoing a dynamic
    stall.



    FULL STORY ==========================================================================
    Wind energy relies on efficient wind turbine blades, which act as
    airfoils, structures akin to an airplane wing. Air flow control
    accessories similar to those found in aircraft improve the turbine
    blade's aerodynamic performance.


    ==========================================================================
    In the Journal of Renewable and Sustainable Energy, by AIP Publishing, scientists from China show a bionic approach combining features of a
    seagull's wing with an engineered flow control accessory, known as a
    Gurney flap, can greatly improve wind turbine performance.

    A Gurney flap is a small tab projecting at right angles from the
    trailing edge of a wing. Its presence disturbs wind flow patterns and is especially effective at improving performance at low angles of attack. In aerodynamics, the angle of attack is the angle between a line through
    the center of an aircraft wing and the oncoming flow of air.

    Although Gurney flaps improve performance of airfoils at low attack
    angles, they are not ideal for large angles of attack. Research has
    shown although Gurney flaps can significantly improve the performance
    of wind turbines in some situations, the turbine speed will be reduced.

    Bionic flow control is a relatively new approach that imitates biological flight control systems -- in other words, wings and feathers. The idea
    comes from the observation that during landing or in a gust of wind,
    the feathers on the top of a bird's wings will pop out, creating a
    natural flap.

    Computational and experimental studies show bionic feather-inspired
    flaps can increase lift and delay the onset of stalling at high angles
    of attack. Despite their advantages, adding bionic flaps can also reduce
    lift, particularly before a stall sets in. Therefore, the investigators
    tried an approach combining Gurney flaps with bionic features.

    To achieve the best aerodynamic performance, the scientists simulated the
    use of the combined flow control accessory in a variety of situations, including high and low angle of attack and pre- and post-stall
    scenarios. They compared their computational simulations to experimental results for an aircraft wing undergoing a dynamic stall.

    "The overall trend of the calculated lift curve is in good agreement
    with the experimental measurement results. Therefore, our simulation
    accuracy is considered acceptable, because the dynamic stall and its
    control are notoriously difficult to predict," author Xiaomin Liu said.

    The combined flow control accessory effectively improves the lift
    coefficient of the airfoil according to Liu. "For angles of attack in
    the range 16 to 24 degrees, the maximum lift coefficient of the airfoil
    is increased by 15% when a combination of Gurney flap and bionic flap
    is used."

    ========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Liming Wu, Xiaomin Liu, Yang Liu, Guang Xi. Using the combined flow
    control accessory to the aerodynamic performance enhancement of bio-
    inspired seagull airfoils. Journal of Renewable and Sustainable
    Energy, 2022; 14 (2): 023302 DOI: 10.1063/5.0079060 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220322111341.htm

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