D300mm×3420mm圆管内旋转流流场的LDV实验测量

利用激光多普勒测速仪（LDV）对直径D300mm×3420mm圆管内的旋转流场进行了实验测量，重点测量切向速度与轴向速度的分布以及湍流强度分布。测量结果表明圆管内的旋转流是Rankine涡结构形态，旋转流强度沿轴向存在着明显的衰减特性，且最大切向速度的径向位置沿轴向逐渐向内移动，即由上游的刚性涡逐渐向下游的准自由涡和刚性涡组合过渡；轴向速度的分布存在着很大的不均匀性，在r=0．5R区域存在一个轴向速度的低速区，甚至出现上行，但在轴向位置z〉10R后轴向速度全部向下，并向均匀分布发展；圆管内的切向湍流强度比轴向湍流强度大一倍，两者的湍流强度在准自由涡区径向分布比较平均，中心刚性涡区域的湍流强度比较高，而且随轴向位置的变化衰减不明显。

Measurement of the swirling flow field in the circular pipe with the diameter 300mm × 3240mm by LDV

The flow field in the circular pipe with the diameter 300mm and the length 3420mm was measured by laser Doppler velocimeter （ LDV）. The distribution of the tangential and axial velocities and the turbulence intensity were obtained. The results show the tangential velocity distribution exhibites the expected combination of the Rankine type vortex ： the inner forced vortex and the outer free vortex. The intensity of the swirling flow has the obvious attenuation characteristic along the axial position and the radial position of the maximum tangential velocity in the cross section gradually moves towards the geometrical center of the circular pipe, namely the upstream forced vortex gradually transits to the combination of the quasi-free vortex and the forced vortex in the downstream. And the axial velocity distribution presents non-uniformity and reveals a low speed area in the r = 0.5 R region, even the axial velocity appears upward. But the axial velocity is completely downward in the region below z 〉 10R and developing to the even distribution. The tangential and axial turbulence intensities have the identical magnitude. The radial distributions of them are quite average except in the central region and basically invariable along the axial position.