Numerical Investigation of Added Mass and Hydrodynamic Damping on a Blunt Trailing Edge Hydrofoil

Abstract

Added mass and hydrodynamic damping play significant roles in fluid-structure interaction (FSI) in hydraulic turbines. Added mass can reduce natural frequencies, while hydrodynamic damping could result in a higher amplitude decay speed of the vibration. In order to quantify the added mass and hydrodynamic damping of a three-dimensional (3D) NACA 0009 hydrofoil with a blunt trailing edge, a two-way FSI simulation method was employed. The effects of grid scale, time-step, turbulence model, exciting force, and numerical damping on the calculation accuracy of the two-way FSI numerical simulation were analyzed in great detail through comparison with the previously published experimental data. Hydraulic force was obtained by using a transitional shear stress transport model at the flow region of the Reynolds number ReL = 0.2 × 106–2 × 106. The vortex shedding frequency, the natural frequency of the first-order bending mode in water, and the hydrodynamic damping ratio obtained from the numerical simulations agree well with the experimental data, with maximum deviations in 6.12%, 4.53%, and 8.82%, respectively. As the flow velocity increases, the natural frequency may not significantly change, while the added mass coefficient gradually increases, considering the effect of added stiffness. Above the first-order bending mode lock-in region, the results indicate that the first-order bending mode hydrodynamic damping ratio increases linearly with velocity. The present numerical achievements offer a higher level of accuracy for predicting the added mass and hydrodynamic damping characteristics of a hydrofoil.