Flow regimes in a cross-shaped channel are studied by Planar Laser Induced Fluorescence at 30≤Re≤350, and a segregated flow, a steady engulfment flow and an unsteady engulfment flow occur in turns with increasing Re. Specially, in the transition regime between steady and unsteady engulfment flow at 230<Re<300, an oscillation characterized by periodic shedding of the vortex ring is identified. Unlike the steady engulfment flow, the center vortex will break into two co-rotating vortices downstream for the vortex shedding oscillation. The fluid residence time in the cross-shaped channel is quantitively assessed. The formation of recirculation regions leads to the increase of the fluid residence time at Re≈110, while the fluid residence time is dramatically reduced at Re>230 due to the shedding of vortex ring. Simulation results reveal that the oscillation is non-axisymmetric and the vortex ring is periodically generated from recirculation regions and propagated downstream, which is ascribed to vortex breakdown.

流动状态在交叉形通道进行了研究由平面激光诱导荧光在30≤重新≤350，和一个分离流，一个稳定的流吞噬和非定常流吞噬发生在随匝再。特别地，在230 < Re <300的稳定和非稳定吞噬流量之间的过渡状态中，确定了以涡旋环周期性脱落为特征的振荡。与稳定的吞噬流不同，中心涡旋将在下游分裂为两个同向旋转的涡旋，从而使涡旋脱落。定量评估十字形通道中的流体停留时间。回流区域的形成导致Re处流体停留时间的增加≈110，而由于涡流环的脱落，流体的停留时间在Re > 230时大大减少。仿真结果表明，该振荡是非轴对称的，涡流环是从再循环区域周期性产生并向下游传播的，这归因于涡流的破裂。