起旋器内部的流速场和涡量场特性

Characteristics of velocity field and vorticity field in generator

为解决低压管道灌溉中存在的含沙水流淤堵管道的问题,采用了低压管道灌溉的螺旋流输水方式.起旋器是产生螺旋流的主要装置,通过理论分析与试验探索,在起旋器内部通道设置了4个测试断面,并对各测试断面内螺旋流的水力特性进行研究.结果表明:导叶对起旋器内部的流速场和涡量场都有重要影响.在不同半径的柱面上,导流片曲线段区域流速变化较大,且越靠近圆管边壁流速变化越强烈.在相同半径的柱面上,轴向流速变化最大,周向流速变化次之,径向流速变化最小.在导叶的进口产生涡旋,继而涡量不断增加并向无导流片区域扩散,形成了涡量密集区且在有导流片的区域,越靠近圆管边壁涡量变化越快.同时用罗斯比数与埃克曼数的大小来反映水流通过起旋器时水流旋转的强烈程度.起旋器内螺旋流涡量场中罗斯比数小于1,埃克曼数量级为10-6～10-5,表明水流通过起旋器时旋转较为强烈.

In order to solve the problems of pipe blockage of the sediment laden flow in low-pressure pipe irrigation,a spiral flow water-conveying method was adopted in the low-pressure pipe irrigation.The generator was the key device to generate the spiral flow.Through theoretical analysis and experimental exploration,four testing sections were designed in the generator inner aisle and the hydraulic characteristics of the spiral flow in each testing section were studied.The results show that the guide vanes have significant influence on the velocity field and the vorticity field in the generator.In different radial cylinders,the velocity changes greater in the curve segment of the guide vane,and the closer it is to the pipe wall the greater the velocity changes.In the same radial cylinder,the variations of the axial velocity are the largest,while those of the circumferential component take second place and those of the radial component are the smallest.The vortex happens at the entrance to the guide vane.Then the vorticity increases constantly and diffuses to the region without guide vanes.The dense area of the vorticity is formed and at the existing region of guide vanes,and the closer it is to the pipe wall the greater the vorticity changes.Meanwhile,the rotational violent degree was described by the values of Rossby number and Ekman number when the water flow goes through the generator.The Rossby numbers are less than 1 and the magnitudes of Ekman number lie between 10-6 and 10-5 in the vorticity field of the spiral flow in the generator.It shows that the rotational violent degree is greater while the water flow goes through the generator.