共轴式双旋翼尾迹流场的水洞PIV测量

采用粒子图像测速(PIV)技术,对共轴式双旋翼在悬停和以不同前进比前飞时的流场进行水洞实验.将激光片光定位于旋翼的纵向截面,桨叶的方位角和图像的获取是同步的.测量得到了旋翼流场的瞬时涡量和速度分布、桨尖涡的结构和脱落轨迹、悬停时的尾迹边界收缩和前飞时的尾迹边界倾斜角等.研究了不同状态下共轴式双旋翼流场的气动干扰特性.为了比较,对单旋翼也进行了同样的测量.实验得到了有价值的结果,对共轴式直升机的气动计算和合理设计具有重要意义.

PIV measurements in the wake of coaxial-rotor in water tunnel

Particle image velocimetry(PIV) technique was applied to the experiment of coaxial-rotor in hover and in forward flight in water tunnel.The laser sheet was positioned for tip vortices shed at zero and 180 degrees azimuths.The rotor rotation and the imaging system were synchronized to acquire PIV images at specified rotor azimuth angles.Instantaneous vorticity and velocity distributions of the rotor flow fields were obtained.The tip vortices were tracked from their generation to convection downstream.The wake contractions in hover and the wake boundary inclination angles in forward flight were measured.The wake geometries and aerodynamic interaction characteristics of coaxial-rotor flow fields were investigated.For comparison,single-rotor flow fields were also measured.The agreement of the experimental results with the literatures indicates PIV is effective to investigate complex flow fields in water tunnel.The valuable results have important meanings to the aerodynamic calculation and reasonable design of coaxial-rotor helicopter.