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首页> 外文会议>41st AIAA fluid dynamics conference and exhibit 2011 >Fluid Dynamic Forces on Plunging Spanwise-Flexible Elliptical Flat Plates at Low Reynolds Numbers
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Fluid Dynamic Forces on Plunging Spanwise-Flexible Elliptical Flat Plates at Low Reynolds Numbers

机译：低雷诺数下切入横向弹性柔性椭圆平板的流体动力

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摘要

We consider the aerodynamic performance of flexible isotropic elliptical wings undergoing periodic plunge motions. Experiments were conducted in the Low Turbulence Water Channel at the University of Michigan using a pitch-plunge apparatus. Experimental results include dye flow visualization, laser Doppler vibrometer (LDV) wing deformation measurements, particle image velocimetry (PIV) flow field quantification, and direct force measurements establishing a novel experimental framework for investigating pitching-plunging and flapping flexible wings. This investigation focuses on the effect of wing stiffness parameter, Π_1, defined as the ratio of elastic to fluid dynamic forces. A parameter sweep is performed that spans four orders of magnitude from order 10~1 to 10~4. The Π_1-parameter is varied by changing the plate thickness and material properties. The effects of structural density to fluid density, ρ, and the thickness to chord ratio, h_s, are shown to be small. The wings have elliptical planform with aspect ratio 6.1. Sinusoidal plunging kinematics are used in forward fight at a low Reynolds number (5,300) with a neutral mean effective angle of attack. The plunging motion has large reduced frequency (1.82) and modest chord-normalized plunge amplitude (0.175). Deformation measurements show that for the present conditions the wings bend without twisting. PIV measurements at the 50%- and 75%-spanwise locations show that large deflections at the wing tip result in a stronger outboard leading edge vortex due to the increased effective angle of attack for increased flexibility. The force measurements proved that the prescribed parametric configuration is not thrust producing due to small wing cross-sectional thickness, motion kinematics, and lack of aerodynamic-twist. The lift (normal) force coefficient for moderate wing stiffness parameter (Π_1 of order 10~2) is larger compared to the rigid wing results. The most flexible wing produced a lift coefficient history below the rigid wing and lags the rigid wing phase. For the rigid cases the force measurements show good agreement with quasi-steady two-dimensional potential flow theory, suggesting that for the present conditions tip vortex effects are small.
机译：我们考虑了经历周期性下降运动的各向同性椭圆形椭圆机翼的空气动力学性能。使用变桨装置在密歇根大学的低湍流水道中进行了实验。实验结果包括染料流动可视化，激光多普勒振动计（LDV）机翼变形测量，颗粒图像测速仪（PIV）流场量化和直接力测量，从而建立了一种新的实验框架，用于研究俯仰俯仰和拍打柔性机翼。这项研究的重点是机翼刚度参数_1_1的影响，该参数定义为弹性与流体动力之比。执行的参数扫描范围从10到1到10到4到4个数量级。通过改变板的厚度和材料特性来改变_1_1参数。结果表明，结构密度对流体密度ρ和厚度与弦长比h_s的影响很小。机翼呈椭圆形，长宽比为6.1。正弦下降运动学用于低雷诺数（5,300），中性平均有效攻角的正向战斗中。跳入运动具有大的降低频率（1.82）和适度的弦归一化跳入幅度（0.175）。变形测量表明，在当前条件下，机翼弯曲而没有扭曲。在跨度分别为50％和75％的位置进行的PIV测量表明，由于增加了有效攻角以提高灵活性，因此机翼尖端的大挠度会导致更强的外侧前缘涡流。力的测量证明，由于机翼横截面厚度小，运动运动学和缺乏空气动力扭曲，规定的参数配置不会产生推力。相较于刚性机翼，中等机翼刚度参数（Π_1约为10〜2）的升力（法向）力系数更大。最灵活的机翼在刚性机翼下方产生升力系数历史，并落后于刚性机翼阶段。对于刚性情况，力的测量结果与准稳态二维势流理论显示出良好的一致性，这表明在当前条件下，尖端涡流效应很小。

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  • 来源
  • 会议地点 Honolulu HI(US)
  • 作者

    Jonathan M. Rausch; Luis P. Bernal; Carlos S. Cesnik; Wei Shyy; Lawrence Ukeiley;

  • 作者单位

    Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI, 48109;

    Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI, 48109;

    Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI, 48109;

    Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI, 48109 Department of Mechanical Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong;

    Department of Mechanical and Aerospace Engineering, University of Florida, Shalimar, FL, 32579;

  • 会议组织
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 流体动力学;
  • 关键词

    AR: aspect ratio; et al;

    机译：AR：长宽比；等;

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