Resonance assessment of a hydrofoil by considering hydrodynamic damping ratio under continuously varying inlet velocity

The variable-speed operation of pumped-storage units increases the resonance risk of blade-like structures. In this study, the blade was simplified to a hydrofoil, with a focus on the hydrodynamic damping ratio (HDR) and vibration behaviors near the resonance velocity (v_r), based on experiments and simulations. Four variable velocity processes were applied as inlet boundary conditions in the computational domain, and the results indicated that the Strouhal number remained nearly unchanged. A very interesting resonance of the flow field was captured when the vibration frequency of the hydrofoil coincided with the vortex shedding frequency, resulting in the pressure pulsation increasing to 2.34 times. A sudden drop in HDR was observed near v_r, with the flow mechanism explained as a reduction in the normal force acting on the hydrofoil. Subsequently, a one-way fluid-structure interaction (FSI) strategy for resonance assessment was developed, considering fluid-added mass and HDR. The v_r was calculated with an error of 2.42 % by comparing it to the experimental data, and both the deformation and equivalent stress at v_r were quantitatively determined. This study enhances the understanding of vortex shedding and HDR characteristics during resonance, providing an effective strategy for assessing resonance risks in blade-like structures.