The peak loads experienced by aircraft of all scales will typically be during gusts, turbulence or extreme manoeuvres. Understanding the aerodynamic response to these transient disturbances is therefore crucial, particularly when Leading-Edge Vortices (LEVs) occur. This fundamental study investigates the aerodynamic response to a wide range of transient plunging motions. The peak loads exhibited a strong dependence to motion amplitude yet remained relatively insensitive to motion duration. Within the parameter range tested (motion duration of T ¡ 20$\tau$, or equivalent reduced frequency k ¡ 1, and plunge amplitude of ${\alpha }_{pl,peak}$ $\le$ 30°), the peak lift did not exceed that of the quasi-static thin airfoil theory prediction, permitting its use as a safe limit for structural design. The normalized peak lift change displayed weak collapse with the timescale of the motion and instead showed better correlation with the non-dimensional plunge rate. The peak pitching moment scales well with plunge rate according to the theoretical prediction due to the added-mass component for plunge-up motions, but quickly diverges for plunge-down motions. At post-stall angles of attack, large-scale vortex shedding was observed and caused decaying oscillations in the loads long after the transient motion ends. For both a NACA 0012 and flat plate airfoil, the first vortex shedding cycle after the transient motion occurs around the subharmonic of the static shedding frequency. Subsequent shedding cycles then increase in frequency and asymptotically approach the static shedding frequency in around 15 to 20 convective times. This is the first study to experimentally quantify this behavior and is an aspect currently missing in existing reduced-order models, which could be significant for the prediction of successive transient disturbances. Finally, Reynolds number insensitivity was demonstrated for transient disturbances between 20,000 and 150,000, even for post-stall angles of attack where large-scale vortex shedding can occur.

所有规模的飞机所承受的峰值载荷通常将在阵风，湍流或极端操纵期间发生。因此，了解对这些瞬态扰动的空气动力学响应至关重要，尤其是在出现前沿涡旋（LEV）时。这项基础研究研究了空气动力学对各种瞬态骤降运动的响应。峰值负荷表现出对运动幅度的强烈依赖性，但对运动持续时间保持相对不敏感。内测试的（运动持续时间参数范围Ť ¡20$\tau$，或等效的降低频率k¡1，以及突降幅度为${\alpha }_{p升，pË\mathrm{一种}ķ}$ $\le$30°）时，峰值升程不超过准静态薄翼型理论的预测值，因此可以将其用作结构设计的安全极限。归一化的峰值升程变化在运动的时间尺度上显示出较弱的塌陷，而与无量纲下降率显示出更好的相关性。根据理论预测，由于俯仰运动的附加质量分量，峰值俯仰力矩随俯冲率很好地缩放，但对于俯冲运动，峰值俯仰力矩迅速发散。在失速后的迎角下，观察到大范围的涡旋脱落，并在瞬态运动结束后很长一段时间内引起了负载中的衰减振荡。对于NACA 0012和平板翼型而言，瞬态运动后的第一个涡旋脱落周期发生在静态脱落频率的次谐波附近。然后，随后的脱落周期会增加频率，并在大约15至20个对流时间内渐近地接近静态脱落频率。这是第一个通过实验量化这种行为的研究，并且是现有降阶模型中目前缺少的一个方面，这对于预测连续的瞬态干扰可能具有重要意义。最后，雷诺数不敏感度在20,000至150,000之间的瞬态扰动中得到了证明，即使在失速后攻角可能发生大规模涡旋脱落的情况下也是如此。这对于预测连续的瞬态扰动可能是重要的。最后，雷诺数不敏感度在20,000至150,000之间的瞬态扰动中得到了证明，即使在失速后攻角可能发生大规模涡旋脱落的情况下也是如此。这对于预测连续的瞬态扰动可能是重要的。最后，雷诺数不敏感度在20,000至150,000之间的瞬态扰动中得到了证明，即使在失速后攻角可能发生大规模涡旋脱落的情况下也是如此。