Radial gate, a spatial frame structure, is the key factor to control water discharge in dam structure and storm surge barriers. However, the fluid-induced vibration (FIV) problem always occurs owing to fluctuation loads exerted on the gate, threatening the safety of hydropower stations. In this work, two fluid–structure interaction (FSI) modal analysis methods—the coupled acoustics–structure method and the added-mass method—are provided. Further, a comprehensive investigation on the vibration characteristics of the spatial radial gate, considering spatial structural characteristics and the FSI effect, is conducted. The numerical results revealed that the feasibility of the proposed coupled acoustics–structure method in analyzing FSI modal analysis was demonstrated; moreover, a reasonable length of the fluid domain in front of the skinplate existed for efficient computation. Meanwhile, through the added-mass method, the rational added-mass discount factor of hydrodynamic loads obtained from the Westergaard formula was provided. The FSI effect induced whole-gate rotation vibration streamwise around trunnion pins, significantly reducing the gate’s fundamental vibration frequency. In addition, three typical dynamic-instability vibration patterns of radial gates were presented. These patterns were affected by spatial structural characteristics and FSI. It was demonstrated that the struts and skinplate coupled bending–torsional vibration would cause the radial gate frame structure to fail catastrophically. The proposed insights can provide guidelines of vibration characteristics analysis of the radial gate submerged in flow water in reservoir and storm surge barriers.

Hydraulic steel gates are the core adjustment mechanism for water conservancy projects, the safety of which is related to the safety of the entire water conservancy project. In this study, the issue of flow-induced vibration under the influence of pulsing water pressure when the deep-hole plane steel gate construction is partially opened is investigated using a numerical calculation approach of CFD–CSD coupling. The time-history pulsating pressure loads of each part are first determined by tracking the upstream, bottom, and downstream pulsating water pressure loads under partially open operation conditions of the gate. The impact of the water in front of the gate on the natural vibration mode and frequency of the gate is then investigated based on the analysis of the dry/wet modes of the gate structure. Additionally, the hydrodynamic load is applied to the finite element model of the gate structure while taking into account the fluid–structure coupling effect, and the results of the gate flow-induced vibration response are obtained. Three typical local opening relative openings are chosen, with the operating state of the design water head (Hs = 70 m) of a deep-hole plane steel gate as an example. According to the analysis’s findings, the gate’s natural vibration frequency is greatly lowered under the influence of the water in front of it, and its amplitude increases by 50%. The pressure value pressing on the gate changes dynamically as it is partially opened and discharged. The maximum dynamic displacement value and the maximum dynamic stress value of the gate both appear in the middle and lower part of the gate under the condition of partial opening, and both occur when the relative opening is e/H = 0.125. The maximum displacement value is 3.43 mm, and the maximum stress value is 161 MPa. The maximum dynamic displacement and dynamic stress of each gate component steadily decrease with an increase in the relative openness. The gate dynamic response analysis approach described in this research can serve as a guide for hydraulic engineering design.