机翼极限环颤振的CFD/CSD全隐式紧耦合方法

针对轴承振动实时状态监控的需要，从符号动力学角度提出了符号聚合近似与Lempel-ziv复杂度（SAX-LZC）融合的振动监控参数。首先，以Logistic映射和Duffing方程为对象，从理论角度验证了SAX-LZC对动力学结构表征的准确性，并验证了该指标的抗噪能力和计算效率；其次，将SAX-LZC指标与信息熵、样本熵、多分段Lempel-ziv复杂度等动力学参数性能进行了综合对比；最后，从实验角度对轴承早期微弱异常进行了监测，并对轴承典型故障进行了特征提取。理论研究结果表明，SAX-LZC具有动力学结构表征准确、抗噪能力好、计算高效简洁等优点，克服了常规动力学参数工程应用能力弱的问题。实验研究结果表明，SAX-LZC对早期微弱异常有准确的监测，对不同种类故障具有较好的区分度，弥补了时域和频域对轴承微弱故障表征能力不足的缺陷，是一种轴承振动实时状态监控与故障特征提取的有效参数。

CFD/CSD Fully Implicit Tightly Coupled Studyon Limit Cycle Flutter of Wing

A fully implicit tightly coupled numerical method is developed for the limit cycle flutter of the wing. The Roe scheme and dual time stepped method are adoptedin the spatial and time discretization of flow field, respectively. The Newmark method based on the finite element method is adopted in the structural transient response. The geometrical nonlinearity of the wing under the large deformation is also considered, and the implicit time marching scheme is used in theanalyses of flow field and structure.On the basis of the traditional loosely coupled method, the pseudoiteration is added in the tightly coupled method.When the pseudo-iteration converges, the physical iteration related to the real time step is sequentially analyzed, which can reduce the time lag effect caused by the frozen boundary conditions in the analysis of traditional loosely coupled method.The transonic limit cycle flutter of the cropped delta wing is also analyzed. The results show that the limit cycle flutter amplitude and the frequency of wing tip obtained by the tightly coupled method are better than the traditional loosely coupled method,closer to the test results.Therefore, the tightly coupled method can eliminate the accumulated errors inthe time marching and has a higher coupled time precision.