应用PIV测量缩比共轴双旋翼流场特性的研究

采用粒子图像测速(Particle image velocimetry,PIV)技术对一缩比共轴双旋翼模型在悬停和以不同前进比前飞时的流场进行水洞实验。测量得到了旋翼流场的瞬时涡量的速度分布,桨尖涡的脱落轨迹,悬停时的尾迹边界和前飞时的尾迹边界等流场特性参数分布。研究了不同状态下共轴双旋翼流场的气动干扰特性。在悬停时,下旋翼的桨尖外侧有上洗流现象,而下旋翼则没有。与共轴双旋翼性能试验数据比较得出,在悬停时共轴双旋翼形式存在有利的相互气动干扰现象。实验还得出了悬停和不同前进比前飞时桨尖涡的脱落轨迹。

PIV Measurements of Model Scale Coaxial Rotors Flow Features

Experimental investigations of model scale coaxial rotors in hover and in forward flight are carried out in water tunnel by particle image velocimetry (PIV) technique. The distributions of instantaneous vorticity and velocity of the rotor flow field are obtained. At the same time, the trajectory of the tip vortex, the wake contractions in hover and in forward flight, and the radial distribution of induced velocity are measured. The wake geometries and aerodynamic interaction characteristics of coaxial rotor flow field are also investigated. Upwash happens at the outboard edge of the blade tip of the lower rotor, while no such phenomenon happens near the upper rotor blade tip. From comparisons with the prior performance experiments, it can also be found that mutual interferences are playing a positive role in the coaxial rotor configuration when hovering. Furthermore, the tip vortex trajectories of the single rotor and coaxial rotor are achieved during the experiment, in hover and at different forward flight ratios, respectively.