The Formation and Evolution of Turbulent Swirling Vortex Rings Generated by Axial Swirlers
The Formation and Evolution of Turbulent Swirling Vortex Rings Generated by Axial Swirlers
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DOI：
10.1007/s10494-019-00076-2
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发表时间：
2019-11
期刊：
影响因子：
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通讯作者：
Chuangxin He;L. Gan;Yingzheng Liu
中科院分区：
文献类型：
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作者：
Chuangxin He;L. Gan;Yingzheng Liu
采用平面粒子图像测速技术（PIV）和大涡模拟（LES）研究了湍流旋转涡环的形成过程和早期演化。涡流环是在活塞-喷嘴布置中产生的，涡流是在实验中由3D打印的轴向旋流器产生的。在大涡模拟中采用理想固体旋转的方法，研究了喷管出口速度分布对大涡模拟的影响。基于喷嘴直径D和喷嘴中的段塞速度U 0的雷诺数（Re）为20，000。旋流数Sgenerated的范围从0（零旋流涡环）和1.1，涵盖了两个临界旋流数先前确定的旋流射流。PIV和LES结果均表明，形成数F随S的增加而线性减小，在S = 0时F最大为2.6（直叶片旋流器产生的），在S = 1.1时F最小为1.9。在喷嘴轴线平行平面内相应的最大可达环量也随S的增大而减小。由冲程比L/D= 1.5产生的致密环的演化表明，环流衰减率与S成正比。涡核在轴向的运动轨迹随S的增大而减小，涡核的轴向传播速度随S的增大而减小，而涡核的径向运动轨迹随S的增大而增大，涡核的径向传播速度随S的增大而增大。提出了一个经验尺度函数来衡量这些变量。
The present work investigates the formation process and early stage evolution of turbulent swirling vortex rings, by using planar Particle Image Velocimetry (PIV) and Large Eddy Simulation (LES). Vortex rings are produced in a piston-nozzle arrangement with swirl generated by 3D-printed axial swirlers in experiments. Idealised solid-body rotation is applied in LES to evaluate the effect of nozzle exit velocity profile in experiments. The Reynolds number (Re) based on the nozzle diameterDand the slug velocityU0in the nozzle is 20,000. The swirl numberSgenerated ranges from 0 (zero-swirl vortex ring) and 1.1, covering the two critical swirl numbers previously identified in a swirling jet. Both PIV and LES results show that the formation numberFdecreases linearly asSincreases, with the maximumF≈ 2.6 atS= 0 (produced by the swirler with straight vanes) and minimumF= 1.9 atS= 1.1. The corresponding maximum attainable circulation in the nozzle axis parallel plane also diminishes with increasingS. Evolution of compact rings produced by a stroke ratioL/D= 1.5 reveals that circulation decay rate is largely proportional toS. The trajectory of the vortex core in the axial direction, hence the ring axial propagation velocity, decreases asS, while that in the radial direction and the radial propagation velocity, increase withS. An empirical scaling function is proposed to scale these variables.