索膜结构风致流固耦合气动阻尼效应研究

Numerical calculation on wind-induced damping of membrane structure based on fluid-structure interaction

根据三角形重心坐标系原理提出了基于松耦合计算的流固耦合网格协调插值新方法,提高了流固耦合的计算效率;为解决由于柔性结构加速度过大而导致的求解不稳定问题,通过在1个时间步上进行流体及结构间反复交替求解来得到稳定的时程解。应用上述方法对一柔性平屋盖结构进行风振响应的数值模拟计算,通过与风洞试验的对比验证了计算结果的可靠性,并较全面地再现结构在风作用下的实际行为。在此基础上,联合采用经验模态分解法(EMD),随机减量法(RDT)和希尔伯特变换法(HT)从结构的动力响应时程数据中提取到了结构的气动阻尼特性信息。分析结果表明,气动阻尼在柔性结构的风振响应中作用不容忽视,主要表现为:四周封闭建筑的阻尼比远小于迎风面开孔建筑的阻尼比,且四周封闭状态下气动阻尼随风速变化小,其对总阻尼的影响较小;而迎风面开孔状态下气动阻尼较大且随风速的增大而增大。因此,对于柔性且阻尼较小的结构,特别对于开孔结构,气动阻尼的影响不可忽略。

According to the theory of triangle barycentric coordinate system, a new method was presented to improve the calculation efficiency of the fluid-structure interaction grid coordination interpolation. Aiming at solving the instability problem caused by the large acceleration of flexible construction, solving alternately and repeatedly on the fluid and the construction in one time step was brought effect to acquire stable time history solution. The result of the above method applied in the analog calculation on wind-induced response of a flexible flat roof building was verified to be reliable by comparing with the wind tunnel test result, and it comprehensively demonstrate the actual act of construction under the wind effect. On this basis, empirical mode decomposition, random decrement technique and Hilbert transform were used unitedly to retrieve the wind-induced damping characteristic information of the construction from the dynamic response time history data. The analysis result shows that the damping ratio of all-round-enclosed construction is far smaller than the windward opening construction, and the change of aerodynamic damping with the wind speed in all-round-enclosed condition is small. As a result, the effect of the sum of dampings is comparatively small. On the other hand, the change of aerodynamic damping with the wind speed in windward opening condition is relatively large, and is increased with the increase of wind speed. Thereby, for small damping flexible constructions, especially for openning constructions, the effect of aerodynamic damping is important.