This study focuses on the dynamics of the three-dimensional jet flow issued from a lobed nozzle. Flow field measurements were performed using a split-screen dual-camera tomographic particle image velocimetry (tomo-PIV) system. The lobed nozzle was constructed using three-circle configuration at the nozzle exit, where the ratio of the circular centre offset to the circle radius was $a/b=$0.8. Two high-speed cameras were used with an appropriate combination of prismatic and planar mirrors to split each camera into two views. The Reynolds number was fixed at $\mathit{Re}=$2400, and the circular jet at the same Reynolds number was also measured for comparison. Fourier mode decomposition was used to identify the large-scale structures superposed in the unsteady flow field. The lobe trough in the jet decreased the jet’s width due to the smooth connection between the pipe section and the lobed exit. Turbulence was intensified in the jet shear layer, and the passing fluid puffs in the circular jet instantaneous flow field were also broken in the lobed jet. The successively passing fluid puffs in the circular jet were observed to be the axisymmetric large-scale structure in Fourier modes dominating at $\mathit{St}=$0.39. However, breakdown of the axisymmetric structures was induced by the lobed nozzle at $\mathit{St}=$0.51 and 0.65, and the double helical modes arose at $\mathit{St}=$0.28 and 0.38 (also 0.4) in the shear layer of the jet potential core and interacted with the entire jet column.

这项研究的重点是从有角喷嘴发出的三维射流的动力学。流场测量是使用分屏式双相机断层摄影颗粒图像测速仪（tomo-PIV）进行的。球形喷嘴是在喷嘴出口处采用三圆构造的，其中圆心偏移与圆半径之比为$\mathrm{一种}/b=$0.8。使用了两个高速相机，并将棱镜和平面镜适当组合，以将每个相机分成两个视图。雷诺数固定为$\mathit{回覆}=$2400，并且还测量了具有相同雷诺数的圆形射流用于比较。傅里叶模式分解用于识别在非恒定流场中叠加的大型结构。射流中的波谷槽减小了射流的宽度，这归因于管段和叶状出口之间的平滑连接。射流剪切层中的湍流加剧，圆形射流瞬时流场中的通过的流体膨化在波状射流中也被破坏。观察到圆形射流中相继通过的流体膨化是轴心对称的大规模结构，在傅立叶模式下占主导地位。$\mathit{英石}=$0.39。然而，轴对称结构的破坏是由在$\mathit{英石}=$0.51和0.65，双螺旋模式出现在 $\mathit{英石}=$在射流势能芯的剪切层中为0.28和0.38（也为0.4），并与整个射流柱相互作用。