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Dynamic stall control on flapping wing airfoils

机译：襟翼机翼的动态失速控制

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Flapping wing efficiency is limited by flow separation effects. The time dependent development of a leading edge vortex (LEV) during rapid pitch-up motion of a retreating helicopter rotor blade is known as dynamic stall vortex. Movement of this vortex along the airfoil upper surface first increases lift but later the vortex lifts off the airfoil surface causing strong drag rise, severe nose-down pitching moments, and possibly negative aerodynamic damping. Very similar effects can be observed on flapping airfoils and wings experiencing combined plunging (heaving) motion and pitching motion. With increasing plunge amplitude the flow on the flapping wing starts to separate and concentrated dynamic stall vortices may develop on both upper and lower wing surfaces. Under these conditions it is shown that wing propulsion efficiency is considerably reduced. Recent investigations of dynamic stall control have shown that a strong vortex may be avoided by appropriate airfoil deformation. It will be shown in the present paper that with dynamic airfoil deformation the propulsion efficiency can be improved considerably. The validity of the numerical calculations is first tested against existing data from literature. (C) 2016 Elsevier Masson SAS. All rights reserved.
机译：襟翼效率受到流分离效果的限制。在后退直升机旋翼桨叶的快速俯仰运动期间，前缘涡流（LEV）随时间的变化被称为动态失速涡流。该涡旋沿着翼型上表面的运动首先会增加升力，但随后涡旋会升离翼型表面，从而导致强劲的阻力上升，严重的机头向下俯仰力矩以及可能的负空气动力阻尼。在拍打翼型和机翼同时经历俯冲（升沉）运动和俯仰运动的情况下，可以观察到非常相似的效果。随着插入幅度的增加，襟翼上的气流开始分离，并且集中的动态失速涡流可能会在上下翼表面上形成。在这些条件下，表明机翼推进效率大大降低。动态失速控制的最新研究表明，适当的翼型变形可以避免强烈的涡流。在本文中将显示出，随着动态翼型变形，推进效率可以大大提高。首先根据文献中的现有数据测试数值计算的有效性。 （C）2016 Elsevier Masson SAS。版权所有。

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