An experimental investigation is conducted to understand the flow behavior near a stack in a hybrid thermoacoustic system including resonator and looped-tube. Time-resolved particle image velocimetry measurement is applied to obtain the evolution of the local oscillating flow. Phase-averaged results show two types of vortices in the flow field due to the stack: the primary vortices attaching at the end of stack, and the corresponding secondary vortices propagating with the base flow. Proper orthogonal decomposition is applied to illustrate small-scale fluctuations from the main flow structure. The temporal coefficients show that vortical flow structures vary from one cycle to another, consistent to the great increment of the phase-averaged turbulence kinetic energy during the period with vortical flow structures. With the same input power, the momentum fluctuation is larger at harmonic frequencies. At the same frequency, the turbulence level is nonmonotonic to the input power although the momentum fluctuation increases with the input power.

进行实验研究以了解包括谐振器和环形管的混合热声系统中烟囱附近的流动行为。时间分辨粒子图像测速仪的测量被用于获得局部振荡流的演变。相平均结果显示，由于烟囱，流场中有两种涡流：初级涡流附着在烟囱的末端，相应的次级涡流随基本流传播。应用适当的正交分解来说明主流结构的小规模波动。时间系数表明，涡流结构从一个周期到另一个周期变化，这与具有涡流结构的期间内相平均湍流动能的极大增加是一致的。在相同的输入功率下，动量波动在谐波频率下更大。在相同的频率下，尽管动量的波动随输入功率的增加而增加，但湍流水平对于输入功率而言并非单调的。