Abstract In this work, the interactive process between separation bubble and impinging leading-edge vortices, which is superimposed in unsteady separated and reattaching flows over a finite blunt plate, was experimentally determined. We used an effective recognition strategy based on an offline data analysis by dynamic mode decomposition (DMD) and online DMD computation in a field-programmable gate array (FPGA). The approach was established for phase-locking particle image velocimetry (PIV) measurements of the underlying vortex dynamics. The DMD mode coefficients of wall-pressure fluctuations following the temporal evolution of the corresponding unsteady events clearly reflected the interactive process, in which three consecutive impinging vortices appeared in one period of the separation bubble. The global interactive process between the separation bubble and the impinging vortices was classified into three consecutive processes: an amplification process, a transition process and a preparation process. The phase-averaged PIV measurements revealed the following: (a) During the amplification process, the separation bubble and impinging vortices are in a synchronous enlargement process beginning from the shortest position of the separation bubble at x / D = 3.00 . (b) In both the transition and preparation processes, the interaction was characterized by a flapping separation bubble (which enlarged in the first half of the period and then shrank in the second half of the period) and by the impinging vortices constantly shedding to the downstream region. Finally, the underlying shear layer instabilities and vortex movements of these three interactive processes were analyzed.

中文翻译：

---

有限钝板上分离气泡和撞击涡流之间的相互作用

摘要 在这项工作中，实验确定了分离气泡与碰撞前缘涡之间的相互作用过程，该涡叠加在有限钝板上的非定常分离和重新附着流中。我们在现场可编程门阵列 (FPGA) 中使用基于动态模式分解 (DMD) 和在线 DMD 计算的离线数据分析的有效识别策略。该方法是为基础涡流动力学的锁相粒子图像测速 (PIV) 测量而建立的。相应非定常事件随时间演变的壁面压力波动的DMD模式系数清楚地反映了相互作用过程，其中在分离气泡的一个时期内出现了三个连续的撞击涡流。分离气泡与撞击涡流之间的全局交互过程分为三个连续的过程：放大过程、过渡过程和准备过程。相位平均 PIV 测量揭示了以下内容：（a）在放大过程中，分离气泡和撞击涡流处于同步放大过程，从分离气泡的最短位置在 x / D = 3.00 开始。(b) 在过渡和准备过程中，相互作用的特点是一个扑动的分离气泡（在前半期扩大，后半期缩小）和撞击涡流不断脱落到下游地区。最后，