基于修正湍流冻结假设桥梁断面旋涡脱落分析

Analysis of Vortex Shedding from Bridge Decks Based on Revised Frozen Turbulence Hypothesis

摘要:

结构所受气动力的规律性变化在流场中表现为规律的旋涡脱落现象,而结构尾流中的规律性脱落的旋涡无论是否可以直接被观察到,都可以采用快照正交特征分解方法加以识别.结合了快照正交特征分解方法和小涡分解方法,并通过引入冻结湍流假设的部分假定,可以根据单个时刻的速度场数据获得结构旋涡规律性脱落的频率,并可根据相邻旋涡的距离获得结构的斯脱罗哈数.方柱绕流和某分离双箱桥梁断面尾迹流场的数值模拟验证结果表明,通过此方法计算得到斯脱罗哈数与采样升力系数幅值谱得到的斯脱罗哈数误差较小,因而此方法有较强的实用性.

Abstract:

Periodic Vortex shedding from the structures coincides with the periodic forces on the structures.The vortices in the downstream of the structures can be detected by the method of snapshot proper orthogonal decomposition(POD)whether they can be seen obviously or not.The method in this paper combines the method of snapshot POD and small eddy decomposition methods together with part of the frozen turbulence hypothesis.The vortex shedding frequency can be obtained based on one-single-time velocity map alone through which the Strouhal number of the structure can be derived.Numerical simulation was done based on the examples of the square cylinder and twin box bridge deck.The results show the error is rather small of the strouhal number with that through the Fourier transform of the lift force coefficient,implying that the method is practicable.