Analysis of vortex-induced vibration flow field evolution characteristics for Π-shaped beam based on dynamic mode decomposition
To explore the vortex-induced vibration(VIV)mechanism of Π-shaped bridges and the suppression principle of aerodynamic measures,the dynamic mode decomposition(DMD)method is introduced in con-junction with computational fluid dynamics(CFD)numerical simulation to decouple and comparatively ana-lyze the flow fields under various operational conditions for a given Π-shaped bridge.The results demonstrate that unstable vortices within the square cavity beneath the main girder's lower surface play a significant role in triggering VIV of Π-shaped girders.The installation of two stabilizing plates at quarter points beneath the gird-er effectively divides the cavity into three smaller regions,thereby reducing the formation space for trailing-edge separation vortices,diminishing both the intensity and scale of vortices within the cavity and effectively mitigating VIV.The second-order DMD mode is found to be in-phase with the structural vibration,represen-ting the dominant mode of driving VIV.This mode provides a direct visualization of the primary vortex forma-tion and evolution within the flow field,greatly simplifying the complexity of flow field analysis.The third and fourth DMD modes exhibit clear harmonic relationships with the structure's VIV frequency and can accu-rately capture the high-frequency components of the vortex-induced forces,which is beneficial for a deep un-derstanding of the instantaneous variation characteristics of VIV and the formulation of more refined damping strategies.
Π-shaped beamvortex-induced vibrationdynamic mode decompositionflow field decoupling
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