Mechanism and effect of seal vibration of a radial gate at small opening heights: Fluid-structure interaction simulation

Self-excited vibrations (SEVs) of water seals of hydraulic gates may induce dangerous flow-induced vibration (FIV) of the gate structure at small gate openings, thus revealing the mechanism and impact of seal SEV is crucial. In this study, we simulated the FIV characteristics of a large radial gate by using the three-dimensional fluid-structure interaction (FSI) model, analyzed the SEV mechanism of two seal types by using a one-dimensional theoretical model, and recommended the seal type that is safer by comparing the effects of the common J-seal and Semi-seal types. The simulated FSI features and the theoretical formulation show that the water hammer effect can be considered by a complex coefficient in the vibration equation, which can describe the SEV phenomenon of seals. The increasing seal deformation and hydraulic oscillation are due to the absolute value of the water hammer reflection coefficient at seals exceeding 1.0. The amplified deformation and oscillation, which aggravate overall gate FIV, can be stable when the water hammer reflection coefficient gradually reduces to 1.0. Since the Semi-seal exhibits higher inherent frequencies and limited deformation, its SEV occurs in a smaller range and causes a lower effect on the gate than the J-seal. The deformation amplitude of the gate FIV induced by Semi-seal SEV is reduced by 50% compared to J-seal. Therefore, it is recommended to use the Semi-seal type to reduce the resonance risk of the gate at small openings.