箱梁颤振的数值模拟及气动能量分析

NUMERICAL SIMULATION OF BOX-GIRDERS FLUTTER AND PNEUMATIC ENERGY ANALYSIS

通过风洞试验测试了箱梁的颤振性能,根据流固弱耦合的计算策略并结合动网格技术模拟了箱梁的颤振过程。针对固体模型在流场中的运动受网格尺寸限制且易造成网格变形过大导致计算失败的问题提出了动网格弹簧系数分层设置的解决办法。给出了气流输入到振动模型的气动能量计算公式和模型表面区域气动能量比的定义,并从能量平衡的观点给出了颤振稳定判据。通过对振动模型气动能量特性的研究发现箱梁迎风侧风嘴是气动能量的主要输入部位,并且在一个完整的振动周期内气流输入到振动系统的能量不断增加,从而造成箱梁振动稳定性的丧失。将数值模拟获得的振动断面周围的流场采用了相位平均的方法进行了处理,分析了箱梁颤振状态下尾部旋涡的演化规律。应用本征正交分解技术(POD)分析了箱梁表面压力的空间分布特征。研究结果表明箱梁颤振过程中表面压力的主要组成部分向模型迎风侧的风嘴漂移。

The flutter performance of box girders was tested by wind tunnel experiment. The flutter process of a box girder was simulated according to a fluid-structure weak coupling calculation strategy and dynamic mesh technique. The movement of a solid model in a flow field was restricted by mesh size, and the grid large-deformation often leaded to calculation failure was solved by a layered-setting method of dynamic mesh spring constant. The formula of pneumatic energy inputting to the vibration model was put forward. The ratio of pneumatic energy inputting to different model-surface areas was also defined. From the viewpoint of energy balance, the flutter stability criterion was provided. The research found that the box girder windward side＇s nozzle was the main pneumatic energy absorption area. In a complete oscillation cycle, the energy inputting to the vibration system by air was increased, leading to the loss of vibration stability. The flow field around the vibration section obtained by numerical simulation was analyzed by the phase-averaged method. The vortex evolution near the box girder tail wind nozzle was studied during flutter. The spatial distribution characteristics of box girder surface pressure were investigated by proper orthogonal decomposition technique. The results show that the main component of model surface pressure drift to the windward side nozzle in flutter.