AUTOROTATING WINGS - EXPERIMENTAL INVESTIGATION
AUTOROTATING WINGS - EXPERIMENTAL INVESTIGATION
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DOI：
10.1017/s0022112071002738
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发表时间：
1971-01-01
影响因子：
3.7
通讯作者：
SMITH, EH
中科院分区：
文献类型：
--
作者：
SMITH, EH
对平板绕其横轴的自转运动进行了实验研究。大部分工作是用安装在密歇根大学5×7英尺低速风洞中的机翼完成的。测量包括非定常升力、阻力、角加速度和机翼转速。在水洞中用烟团、簇状物和小模型研究了流型，其流型与静力机翼上的流型有很大的不同。在雷诺数为25000至25000的范围内，测量了雷诺数为25000至25000的最大和平均升力、阻力和角加速度，直到机翼旋转超过零迎角时，机翼才失速，直到几乎垂直于自由气流，气流才重新附着到下表面。在Re=240 000时，最大升力系数为4·50，平均值为2·20；最大阻力系数为4·30，平均值为1·60。角加速度很小；机翼以几乎恒定的角速度旋转。测量了雷诺数在1300~280000范围内的无量纲翼自转速度，并在足够大的雷诺数下接近0·35的渐近极限，研究了施加驱动力矩和阻尼力矩对机翼的影响。当旋转速度增加到自由自转速度以上时，升力和阻力增加。当转速被阻尼力矩降低时，它们都减小了。旋转翼产生的功率比相同前缘区域的风车小得多。测试了各种翼型，包括不同的翼型和展弦比，以及安装在机翼不同位置的扰流板。然而，除了大到阻止自转的扰流板外，这些变化都没有对自转现象的总体特性产生重大影响。在雷诺数大于4000的情况下，平均升力系数和阻力系数与定轴试验中观测到的结果相当，且流型相似。
The autorotation of a flat plate about its spanwise axis was experimentally studied. Most of the work was done with a wing mounted in the University of Michigan 5 × 7 ft low-speed wind tunnel. The measurements consisted of the unsteady lift, drag, angular acceleration and the wing rotation rate. The flow pattern was studied by means of smoke, tufts and a small model in a water tunnel.The flow pattern was very different from that over a static wing. The wing did not stall until it was nearly perpendicular to the free stream and the flow did not reattach to the lower surface until the wing had rotated well past zero angle of attack.The maximum and average lift, drag and angular acceleration were measured for Reynolds numbers from 25 000 to 250 000. At Re = 240 000 the maximum lift coefficient was 4·50 with an average value of 2·20, while the maximum drag coefficient was 4·30 with an average value of 1·60. The angular acceleration was small; the wing rotated at an almost constant angular velocity. The non-dimensional wing rotation rate was measured for Reynolds numbers from 1300 to 280 000 and approached an asymptotic limit of 0·35 for sufficiently high Reynolds numbers.The effect of applying driving and retarding torques to the wing was studied. As the rotation rate was increased above the free autorotation rate, the lift and drag increased. When the rotation rate was reduced by a retarding torque they both decreased. The power developed by the rotating wing was considerably less than for a windmill of the same frontal area.A variety of wing configurations were tested, including different airfoils and aspect ratios and spoilers mounted at various locations on the wing. However, except for spoilers that were so large that they prevented autorotation, none of these changes had a major effect on the gross properties of the autorotation phenomenon.Freely falling wings were also studied. For Reynolds numbers above 4000 the average lift and drag coefficients were comparable to those observed in the fixed axis tests and it appeared that the flow pattern was similar.