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Prediction and Fundamental Understanding of Stall Loads in UH-60A Pull-up Maneuver

机译：UH-60A上拉机动中失速载荷的预测和基本理解

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This paper identifies and isolates the physics governing the aerodynamics and structural dynamics of UH-60A rotor in unsteady maneuvering flight by studying them separately. For identification of prediction deficiencies in each, first, the measured lift, drag, pitching moment and damper force from the UH-60A Flight Test Program are used to obtain an accurate set of deformations. Second, the resultant blade deformations are used to predict the airloads using lifting-line and CFD aerodynamic models. Both lifting-line as well as CFD analyses predict all three stall cycles with prescribed deformations. It is concluded that advancing blade transonic stall, observed from revolution 12 onwards, is a twist stall triggered by 5/rev elastic twist deformation. The 5/rev elastic twist is triggered by the two retreating blade stalls from previous revolution, which are separated by 1/5 rev. The accurate prediction of both stall cycles on retreating blade holds the key to prediction of advancing blade stall. In analysis, advancing blade stall is triggered by a correct combination of control angles and 5/rev elastic twist. Similar to steady flight, some discrepancies are observed in higher harmonics of torsion, which are not resolved by using measured airloads.
机译：本文通过对UH-60A转子在非稳态机动飞行中的空气动力学和结构动力学的控制进行识别和隔离，将它们分开研究。为了确定每种预测的缺陷，首先，使用UH-60A飞行测试程序测得的升力，阻力，俯仰力矩和阻尼力来获得一组精确的变形。其次，使用提升线和CFD空气动力学模型，将所得叶片变形用于预测空气负荷。提升线和CFD分析都可以预测所有三个停顿周期，并具有规定的变形。可以得出结论，从转数12开始观察到，前进的叶片跨音速失速是由5 / rev弹性扭曲变形触发的扭曲失速。 5 / rev弹性扭曲由前一转的两个后退叶片失速触发，它们之间的间隔为1/5 rev。后退叶片失速周期的准确预测是预测叶片失速提前的关键。在分析中，前进叶片失速是由控制角和5 / rev弹性扭曲的正确组合触发的。与稳定飞行相似，在较高的扭转谐波中观察到一些差异，这些差异不能通过使用测得的空载来解决。

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