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首页> 外文期刊>Journal of the American Helicopter Society >A Full-Scale Rotor-Wake Investigation of a Free-Flying Helicopter in Ground Effect Using BOS and PIV
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A Full-Scale Rotor-Wake Investigation of a Free-Flying Helicopter in Ground Effect Using BOS and PIV

机译：使用BOS和PIV在接地效果中的自由飞行直升机的全尺寸转子调查

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摘要

Measurements in the wake of a free-flying full-scale helicopter in ground effect were performed for both quasi-steady and unsteady maneuvering flights using stereoscopic particle image velocimetry (PIV), a time-resolved background-oriented schlieren (BOS) setup, and an optical marker tracking technique. The systems were used in a complementary way to both visualize blade tip vortices in a large portion of the rotor wake and to capture spatially resolved wake velocity data close to the ground. The high sensitivity of the BOS system enabled the detection of vortices up to an age of ψ = 630°. Different instability mechanisms as long-wave, short-wave, and pairing instabilities were observed with varying intensity for different flight conditions. A quantitative analysis of vortex locations showed a periodic variation resulting from interactions between consecutive vortices that led to vortex pairing. Characteristics of the wake outwash close to the ground were investigated by means of averaged velocity fields. Different patterns such as wall jet, recirculation, and ground vortex flow were quantitatively analyzed and found to be in good agreement with previous model helicopter experiments. The instantaneous velocity data were used to detect individual blade tip vortices with ages above 450° close to the ground and to extract vortex parameters. For a takeoff maneuver, both concentrated vortices and the formation of larger vortex structures due to bundling of several vortices were observed.
机译：在使用立体粒子图像Velocimetry（PIV）的准稳态和不稳定的机动飞行中，对自由飞行的全尺寸直升机进行了测量，用于使用立体粒子图像VELOCIMETRY（PIV），是一项时间分辨的背景导向的Schlieren（BOS）设置，以及光学标记跟踪技术。该系统以互补的方式使用，以便在转子唤醒的大部分中可视化叶片尖端，并捕获靠近地面的空间分辨的唤醒速度数据。 BOS系统的高灵敏度使得检测到ψ= 630°的年龄。观察到不同的不稳定性机制，以不同的飞行条件的强度不同的强度观察到的长波，短波和配对不稳定性。涡旋位置的定量分析显示了由导致涡旋配对的连续涡流之间的相互作用产生的周期性变化。通过平均速度场研究了靠近地面的唤醒液体的特性。定量分析了不同的模式，如壁式喷射，再循环和地涡流，并发现与先前的模型直升机实验吻合良好。瞬时速度数据用于检测具有高于450°高于450°的单独叶片尖端，并提取涡流参数。对于起飞操纵，观察到浓缩涡流和由于捆绑几种涡流而导致的较大涡流结构的形成。

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