不同振动状态下矩形柱体展向相关性和相干结构数值模拟

Numerical Simulation of Spanwise Correlation and Coherent Structures of the Flow Around a Rectangular Cylinder Under Different Vibration States

摘要:

涡激振动具有明显的三维流动特征，主要表现在展向方向上非定常气动力和流动特性不完全同步，且因振动状态而异。以典型桥梁基础断面（5：1矩形）为对象，借助动网格技术开展了不同振动状态下的大涡模拟数值试验，对比研究了涡振发生过程中各关键阶段的气动力和风速展向相关性和相干结构的变化。研究发现：在振动状态变化的过程中气动力和速度的相关性均先增大后减小，但相关系数的最大值并未出现在振幅最大状态；尾流速度的展向相关系数明显小于气动力展向相关系数，在三个速度分量中展向速度的相关系数最小；振动矩形柱体周围流场展向相干结构的尺度比静止状态明显增大。

Abstract:

Vortex-induced vibration （VIV） exhibits distinct three-dimensional flow characteristics， which means that the unsteady aerodynamic forces and flow features in the spanwise direction are not fully synchronized and change with the vibration state. In this study， large eddy simulation （LES） combined with the dynamic mesh technique is employed to investigate the spanwise correlation of aerodynamic forces and velocities， as well as the evolution of the corresponding flow structures around a typical bridge section（a rectangular 5：1 cylinder）under different vibration states. It is concluded that during vibration， the correlation between aerodynamic forces and velocity initially first increases and then decreases， with the maximum correlation coefficient not corresponding to the state of maximum amplitude. The spanwise correlation coefficient of wake velocity is significantly smaller than that of aerodynamic forces， and among the three velocity components， the spanwise velocity exhibits the smallest correlation coefficient. The spanwise correlation structures of the flow field around the vibrating rectangular cylinder have clear larger scales compared to the stationary state.