The Precessing Vortex Core (PVC) is a coherent structure that can arise in swirling jets from a global instability. In this work, the PVC is investigated under highly turbulent conditions. The goal is to characterize the receptivity of the PVC to active flow control, both theoretically and experimentally. Based on stereoscopic particle image velocimetry and surface pressure measurements, the experimental studies are facilitated by Fourier decomposition and proper orthogonal decomposition. The frequency and the mode shape of the PVC are extracted and a very good agreement with the theoretical prediction by global linear stability analysis (LSA) is found. By employing an adjoint LSA, it is found that the PVC is particularly receptive inside the duct upstream of the swirling jet. Open-loop zero net mass flux actuation is applied at different axial positions inside the duct with the goal of frequency synchronization of the PVC. The actuation is shown to have the strongest effect close to the exit of the duct. There, frequency synchronization is reached primarily through direct mode-to-mode interaction. Applying the actuation farther upstream, synchronization is only achieved by a modification of the mean flow that manipulates the swirl number. These experimental observations match qualitatively well with the theoretical receptivity derived from adjoint LSA. Although the process of synchronization is very complex, it is concluded that adjoint LSA based on mean field theory sufficiently predicts regions of high and low receptivity. Furthermore, the adjoint framework promises to be a valuable tool for finding ideal locations for flow control applications.

中文翻译：

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湍流进动涡核的接受度：同步实验和全局伴随线性稳定性分析

进动涡核 (PVC) 是一种连贯的结构，可以在全球不稳定的旋流喷射中出现。在这项工作中，PVC 在高度湍流条件下进行了研究。目标是在理论和实验上表征 PVC 对主动流动控制的接受性。基于立体粒子图像测速和表面压力测量，傅立叶分解和适当的正交分解促进了实验研究。提取了 PVC 的频率和振型，发现与全局线性稳定性分析 (LSA) 的理论预测非常吻合。通过使用伴随的 LSA，发现 PVC 在旋流射流上游的管道内特别容易接受。开环零净质量通量驱动应用于管道内的不同轴向位置，目的是实现 PVC 的频率同步。显示驱动在靠近管道出口处具有最强的影响。在那里，频率同步主要是通过直接模式到模式的交互来实现的。在更远的上游应用驱动，同步只能通过修改操纵涡流数的平均流量来实现。这些实验观察与从伴随 LSA 得出的理论接受度定性匹配。虽然同步过程非常复杂，但可以得出结论，基于平均场理论的伴随 LSA 足以预测高和低感受性区域。此外，