多旋翼近地非定常流动特性

IF 2.8 Q2 MECHANICS
Hasse N.J. Dekker, Woutijn J. Baars, Fulvio Scarano, Marthijn Tuinstra, Daniele Ragni
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引用次数: 0

摘要

实验研究了两个并排转子在近地条件下的非定常流动特性。转子诱导出与地面相互作用的速度分布,引起转子尾迹的径向膨胀。在转子之间,两个尾迹相互作用,产生了类似喷泉的向上流动。检查了两种类型的流动拓扑,并对应于转子和地面之间的两个不同的高度:第一种是喷泉的高度保持在转子圆盘下方,第二种是喷泉出现在转子圆盘上方,被重新吸收。喷泉不稳定性显示增加时,再摄取发生,确定从一个转子盘到另一个位置切换,多次在采集期间。因此,在两个转子上施加可变的流入条件。在比叶片通过频率低约两个数量级的频率上观察到喷泉动力学。主要特征时间尺度与流动再循环路径有关,与推力和地面离地高度的系统参数有关。采用适当的正交分解方法对流场进行了分析,确定了流场的耦合模态。利用模态分析的结果,建立了一个简单的再摄入切换循环的动态流动模型。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Unsteady flow behaviour of multi-rotors in ground proximity
The unsteady flow behaviour of two side-by-side rotors in ground proximity is experimentally investigated. The rotors induce a velocity distribution interacting with the ground causing the radial expansion of the rotor wakes. In between the rotors, an interaction of the two wakes takes place, resulting in an upward flow similar to a fountain. Two types of flow topologies are examined and correspond to two different stand-off heights between the rotors and the ground: the first one where the height of the fountain remains below the rotor disks, and a second one where it emerges above, being re-ingested. The fountain unsteadiness is shown to increase when re-ingestion takes place, determining a location switch from one rotor disk to the other, multiple times during acquisition. Consequently, variable inflow conditions are imposed on each of the two rotors. The fountain dynamics is observed at a frequency that is about two orders of magnitude lower than the blade passing frequency. The dominant characteristic time scale is linked to the flow recirculation path, relating this to system parameters of thrust and ground stand-off height. The flow field is analysed using proper orthogonal decomposition, in which coupled modes are identified. Results from the modal analysis are used to formulate a simple dynamic flow model of the re-ingestion switching cycle.
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来源期刊
CiteScore
2.40
自引率
0.00%
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