风敏感结构流固耦合计算新方法与风致振动机理研究

Fluid-structure interaction (FSI), which poses a significant consideration for the safety of wind-sensitive structures, plays a crucial role in the dynamic effect of these structures. However, the deficiency in complete coupling theories fails to guarantee a deeper insight into mechanisms on wind-induced vibrations. To this end, the present study adopts computational mechanics, numerical methods and computer techniques in order to investigate the numerical techniques, as well as the intrinsic coupling mechanisms, of the FSI effect of complex wind-sensitive structures subjected to strong wind. The unsteady, nonlinear dynamic model of the coupled wind-structure system is established by utilizing the stabilized and smoothed finite element methods from the perspective of arbitrary Lagrangian-Eulerian description. The individual fields are optimized as the basis of the FSI solution. A novel method is developed for modifying interface conditions, which shapes partitioned coupling schemes with low mass ratio. Unified formulations of conservation laws of continua are also derived for casting a matrix-free, factional-step monolithic scheme. The proposed approaches are expected to lead to the better accuracy and the higher efficiency, achieving a breakthrough of available FSI theories. The flow-induced oscillations of the structure due to different incoming winds are analyzed by employing the above model and numerical methods, and in turn the flow characteristics altered by the structural motion are evaluated in detail. The variations of multiple aerodynamic parameters are revealed in consideration of different factors. The vortex shedding modes behind the wake are assessed, which cause the energy transfer from the fluid to the structure and vice versa. The relevant phenomenon and regulations are summarized and interpreted, respectively. The nature of wind-induced vibrations is thus recognized better. Meanwhile several practical criteria are set up to predict the structural damage caused by strong wind. This study is committed to serve the flow-induce oscillation failure of those engineering structures in the complex and changeable wind environment by providing some new ideas and techniques.

流固耦合为制约风敏感结构的关键动力效应，严重威胁结构安全。耦合理论至今尚不完善，故难以更深入认识风振耦合机理。围绕这一难题，本项目基于计算力学理论、数值方法和计算机技术，运用稳定化/光滑有限元方法建立风与结构瞬态耦合的ALE非线性动力模型，研究强风作用下复杂风敏感结构流固耦合作用的数值模拟技术与内在耦合机理。通过优化单场求解策略，构建新型界面修正技术与连续介质守恒律统一公式，旨在提出适应低质量比的分区算法和无矩阵运算的分步型整体算法，探索耦合算法精度不足与效率低下的有效解决途径，突破既有理论局限；基于上述模型与改进方法，确立来风条件对结构振动的影响及动边界对流场的扰动，掌握多气动参数关联变化特征，揭示涡脱落模式转化规律，阐明漩涡耦合结构运动的吸释能机制，进而认清结构风致振动的行为本质，建立实用判断准则实现结构风振破坏预测。研究成果为解决多变风环境下结构流致振动破坏难题提供了新思路和新方法。

流固耦合多发生于各类风敏感土木工程结构，与人类生产生活息息相关。典型现象包括：超高层建筑、高耸结构、大跨桥梁及长径线缆在强/台风作用下出现激烈风致振动。该类结构质量轻、柔性大、阻尼小和自振频率低，受流体（自然风）作用则易发生流固耦合。流致结构振动频率接近其固有频率时，流固耦合系统出现共振，极可能导致灾难性后果。故流固耦合为制约此类工程结构的关键动力效应。本研究着眼应用数学理论、计算力学原理、数值方法和计算机技术，运用稳定化/光滑有限元方法建立任意拉格朗日-欧拉描述下流固耦合体系瞬态非线性动力模型与控制方程，提出改进流固耦合数值求解技术，主要研究内容及创新点总结如下：.（1）改进联合界面边界条件（CIBC）法、构建混合型界面耦合条件：将CIBC修正项转为不含结构拖拽力的一阶常微分方程，避免界面可用于刚体流固耦合；基于完整流体应力张量提出更简洁CIBC界面修正项，无需求解常微分方程；运用广义逆矩阵原理缓解刚体全局修正与局部修正不一致的矛盾。.（2）提升半隐式分区流固耦合算法的效率：运用人工可压缩性修改流体连续方程，每迭代步内仅需计算可压缩系数、避免求解压力泊松方程，且求解精度与完全隐式算法相当，适用于钝体涡激振动问题。.（3）克服光滑有限元法求解Navier-Stokes方程的理论障碍：从数学上严格证明了该方法不依赖高斯散度定理、可求积任意阶导数项，且光滑Galerkin弱式积分与积分点坐标无关，从而适应严重扭曲网格，比传统有限元法更具优势。.此外，本研究还优化了单场求解策略，初步探讨了不同质量比的刚体、柔性体关键气动参数变化特征，揭示涡脱落模式转化现象与结构响应变化。研究成果为工程结构流致振动模拟与预测提供了新思路。