System identification and signal processing for nonlinear aeroelastic systems

本研究计划的目标是开发和验证，数值和实验，一套分析工具，用于识别和表征非线性气动弹性系统，特别关注包含孤立非线性的全局线性系统。这些工具将基于时间、频率和时频，并将用于1)从非关键测试数据中识别非线性气动弹性系统，2)表征气动弹性非线性，以及3)提取线性和非线性系统参数，以预测瞬态、不确定和不稳定行为，如极限环振荡和混沌。该研究项目将数值模拟、实验和分析方法结合到非线性气动弹性系统的模态测试和信号处理中。建立了一个数值模型，可以模拟结构上线性或非线性、二自由度或三自由度的刚性翼型截面的自由和强迫响应。数值模型与风洞试验数据进行了验证，并用于生成一系列翼型构型和几种不同结构非线性参数下的非线性气动弹性响应数据。从模拟中获得的数据将用于设计和扩展风洞试验段的能力，以及开发基于经典傅立叶分析、反向输入/输出分析、恢复力面、光谱仪和其他信号处理技术的信号处理工具。这些工具将适用于非线性气动弹性环境，并用于提取与系统独特非线性行为相关的系统参数信息，以及从稳定到不稳定气动弹性行为的过渡。来自不同工具的输出将被组合起来，以映射系统参数的演变，并研究模式和识别特征，从而能够预测不稳定性。预测结果将通过数值模拟和风洞试验进行验证。该研究结果有望为处理非线性气动弹性和流体/结构系统的不稳定性的工程界提供重要的价值。

The objective of this research program is to develop and validate, both numerically and experimentally, a set of analytical tools for the identification and characterization of nonlinear aeroelastic systems, with a specific focus on globally linear systems containing isolated nonlinearities. The tools will be time, frequency and time-frequency based and will be used to 1) identify nonlinear aeroelastic systems from non-critical test data, 2) characterize aeroelastic nonlinearities and 3) extract linear and nonlinear system parameters in order to predict transient, uncertain and unstable behaviours such as limit cycle oscillations and chaos. The research program combines numerical modeling, experimental and analytical approaches to modal testing and signal processing for nonlinear aeroelastic systems. A numerical model is developed that can simulate the free- and forced-response of a structurally linear or nonlinear, two or three degree-of-freedom, rigid airfoil section. The numerical model is validated against wind tunnel test data and employed to generate data for nonlinear aeroelastic response over a range of airfoil configurations and for several distinct structurally nonlinear parameters. Data obtained from simulations will be used to design and expand the wind tunnel test-section capability as well as develop signal processing tools based on classical Fourier analysis, reverse input/output analysis, restoring force surfaces, spectrographs, and other signal processing techniques. These tools will be adapted to the nonlinear aeroelastic environment and used to extract system parameter information associated with the systems uniquely nonlinear behaviour, and with the transition from stable to unstable aeroelastic behaviour. The ouput from the different tools will be combined to map the evolution of the system parameters, and studied for patterns and identifying features that will enable the prediction of instabilities. Predictive results will be validated with numerical simulations and wind tunnel tests. The results of this research are expected to contribute significant value to the engineering community dealing with instabilities of nonlinear aeroelastic and fluid/structure systems.