悬停状态旋翼非定常尾迹测量

用热线风速仪测量悬停状态旋翼尾迹的轴向、切向速度分量的时均值和瞬时值沿展向的分布及桨尖涡在轴剖面里的运动轨迹，得到了悬停状态旋翼尾迹的几何边值、桨尖涡在运动过程中的耗散和不稳定等非定常特性，研究了旋翼桨距、桨叶片数对悬停状态旋翼尾迹和桨尖涡运动轨迹的影响。结果表明：悬停状态旋翼尾迹轴向速度在其展向的最大值可达或超过动量理论值的两倍；而桨尖涡区域的瞬态值则高达动量理论值的１０倍。旋翼桨距、桨叶片数的

Measurement of Unsteady Wake of Rotor in Hover

Presents the wake unstable characteristics and two component velocities measured with hot wire anemometer. The blade tip vortex trajectory, time averaged velocity distribution along wake radii and instantaneous velocities at a series of distances below the rotor disk are measured. The wake geometry tip vortex expansion and dissipative characteristics are found. The effects of blade pitch and blade numbers on vortex structure, vortex path and wake geometry are studied. The results indicate that the maximum mean induced velocity of the wake exceeded twice the magnitude of momentum theory and that the maximum instantaneous value of vertical velocity component in the vicinity of vortex trails could be as large as ten times of the momentum value of induced velocity. The effects of varying the test parameters are reflected by significant changes of flow within the rotor tip vortex trails and the small variations of velocity components of the inner wake region. The near wake geometry is good in agreement with that of prescribed wake model, the far wake shown up the unstable characteristics.