Department of Mechanical Engineering, Shiv Nadar University, 203207 Greater Noida, India.
School of Engineering, Institute for Energy Systems, University of Edinburgh, Edinburgh EH9 3FB, United Kingdom.
Chaos. 2022 Jul;32(7):073114. doi: 10.1063/5.0096213.
This study focuses on characterizing the bifurcation scenario and the underlying synchrony behavior in a nonlinear aeroelastic system under deterministic as well as stochastic inflow conditions. Wind tunnel experiments are carried out for a canonical pitch-plunge aeroelastic system subjected to dynamic stall conditions. The system is observed to undergo a subcritical Hopf bifurcation, giving way to large-amplitude limit cycle oscillations (LCOs) in the stall flutter regime under the deterministic flow conditions. At this condition, we observe intermittent phase synchronization between pitch and plunge modes near the fold point, whereas synchronization via phase trapping is observed near the Hopf point. Repeating the experiments under stochastic inflow conditions, we observe two different aeroelastic responses: low amplitude noise-induced random oscillations (NIROs) and high-amplitude random LCOs (RLCOs) during stall flutter. The present study shows asynchrony between pitch and plunge modes in the NIRO regime. At the onset of RLCOs, asynchrony persists even though the relative phase distribution changes. With further increase in the flow velocity, we observe intermittent phase synchronization in the flutter regime. To the best of the authors' knowledge, this is the first study reporting the experimental evidence of phase synchronization between pitch and plunge modes of an aeroelastic system, which is of great interest to the nonlinear dynamics community. Furthermore, given the ubiquitous presence of stall behavior and stochasticity in a variety of engineering systems, such as wind turbine blades, helicopter blades, and unmanned aerial vehicles, the present findings will be directly beneficial for the efficient design of futuristic aeroelastic systems.
本研究侧重于刻画非线性气动弹性系统在确定性和随机流入条件下的分岔情景和潜在的同步行为。针对处于动态失速条件下的典型俯仰-纵摇气动弹性系统进行了风洞实验。研究发现，在确定性流动条件下，系统经历亚临界 Hopf 分岔，从而导致失速颤振区域的大幅幅限幅环振荡（LCO）。在这种情况下，我们观察到俯仰和纵摇模式在折叠点附近存在间歇性相位同步，而在 Hopf 点附近则观察到相位捕获同步。在随机流入条件下重复实验，我们观察到两种不同的气动弹性响应：失速颤振期间的小振幅噪声诱导随机振荡（NIRO）和大振幅随机 LCO（RLCO）。本研究表明在 NIRO 区域，俯仰和纵摇模式之间存在异步。在 RLCO 开始时，即使相对相位分布发生变化，异步仍然存在。随着流动速度的进一步增加，我们在颤振区域观察到间歇性相位同步。据作者所知，这是首次报道气动弹性系统中俯仰和纵摇模式之间相位同步的实验证据，这对非线性动力学领域具有重要意义。此外，鉴于各种工程系统（如风力涡轮机叶片、直升机叶片和无人机）中存在失速行为和随机性，本研究结果将直接有益于未来气动弹性系统的高效设计。
