论文标题
层次中的粉扑状不稳定，圆形喷气机的湍流超临界过渡
Puff-like instability in laminar to turbulence supercritical transition of round jets
论文作者
论文摘要
我们使用新型的实验设置和线性稳定性理论（LST）探索了低雷诺数（RE <1000）在低雷诺数（RE <1000）处的圆形喷气机的层流。该设置具有较大的域和低干扰环境，将临界RE增加到大约500，从而允许迄今未知的粉扑状不稳定（PFI）出现。通过清洁流动式可视化（FV）在射流的自相似区域中鉴定出不稳定性，并通过粒子图像速率（PIV）测量进一步证实。对于400 <re <700，该流量表现出嵌入在管道流过渡中的层流流中的PFI中，该pfi被层流的流量封装在pFI中。后者是有限振幅干扰过渡方案的象征。关于PFI对流的观察结果接近局部速度的平均局部速度，进一步增强了类比。 LST预测，PFI实际上是螺旋模式（HM）对具有方位角波数n =+-1的叠加。因此，PFI也可以出现在无穷小振幅的超临界途径中，直到线性不稳定流的过渡。
We explore the laminar to turbulence transition of round jets at low Reynolds number (Re < 1000) using a novel experimental setup and linear stability theory (LST). The setup has a large domain and a low disturbance environment which increases the critical Re to approximately 500, permitting the appearance of a hitherto unknown puff-like instability (PFI). The instability is identified in the self-similar region of the jet through clean flow visualizations (FV) and further corroborated by particle image velocimetry (PIV) measurements. For 400< Re <700, the flow exhibits PFI embedded in a puff-train encapsulated by a laminar flow analogous to 'puffs' in pipe-flow transition; the latter being symbolic of the finite-amplitude disturbance transition scenario. The observation that PFI convects close to the average local velocity with an inflectional velocity profile further strengthens the analogy. LST predicts that PFI is effectively a superposition of the helical mode (HM) pair with azimuthal wavenumbers n=+-1. Hence, PFI can also appear in the infinitesimal-amplitude supercritical route to transition of linearly unstable flows.
