Abstract: Detailed mean velocity distribution of a rotating U-bend duct was measured with LDA.The U-bend duct has a cross section of 50 mm×50 mm,and the ratio of the mean radius of the bend to thd hydraulic diameter of the duct is 0 65,the axis of rotation is parallel to the bend axis.Three cases were investigated:a stationary U-bend duct flow,a case with the U-bend duct rotating positively at a rotation number Ro =0 2,and a case with negative rotation at Ro =-0 2.Flow separation occurs in all three measured cases at the inner wall from half way of the bend to certain downstream region.The size of separation region and the velocity distributions of these three cases are significantly different because the direction and the intensity of the secondary flow are different for different rotation condition.

Key words: Turbulent flow;Rotating fluid;Flow velocity measurement;Laser Doppler velocimeter

摘要： 为了深入了解旋转涡轮叶片内冷通道中的流动特性 ,用激光多谱勒测速仪 (LDA)测量了旋转U型通道中的平均速度分布。通道的横截面积为 5 0mm× 5 0mm ,弯管的平均半径与水利直径的比值为 0 6 5 ,旋转轴与弯管的曲率轴平行。在Re=10 5 时分别测量了转动数Ro =0 ,0 2和 - 0 2三种旋转状态下的速度分布。在这三种情况下弯管内侧θ =90°至下游一定范围内都有流动的分离出现。由于不同的旋转状态二次流的方向和强弱不同 ,导致了分离区大小和通道中速度分布的不同。

关键词: 湍流;旋转流体;流速测量;激光多普勒速度计