Numerical simulations of the effect of leading edge cavitation on the vibration characteristics of an elastic hydrofoil

YAO Zhifeng; LAI Guihua; LIU Jing; ZENG Yongshun

doi:10.16511/j.cnki.qhdxxb.2020.22.043

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Journal of Tsinghua University(Science and Technology) ›› 2021, Vol. 61 ›› Issue (11) : 1325-1333. DOI: 10.16511/j.cnki.qhdxxb.2020.22.043

HYDRAULIC ENGINEERING

Numerical simulations of the effect of leading edge cavitation on the vibration characteristics of an elastic hydrofoil

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Abstract

When hydraulic machinery operating conditions differ from the design conditions, leading edge cavitation can significantly disrupt the flow field and increase fluid-solid interactions (FSI) between the flow and the blade which change the system vibration characteristics. The flow around a NACA0009 elastic hydrofoil was simulated using the shear stress transfer (SST) turbulence model and the Zwart-Gerber-Belamri (ZGB) cavitation model in the three dimensional Reynolds average numerical simulation (RANS) method.The damped natural frequency and the added damping ratio were then calculated using a two-way FSI numerical method. The results were verified against existing experimental data. The computational results show that both the length and thickness of the cavitation region expand and the boundary layer on the hydrofoil leading edge grows thicker as the cavitation number decreases. The increasing cavitation length then reduces the shedding vortex frequency from the hydrofoil trailing edge. The leading edge cavity has little influence on the vibration shape of the bending mode, but greatly influences the vibration shape of the torsional mode. Enlarging the cavitation region increases the natural frequencies of the bending and torsional modes of the elastic hydrofoil in the same way, while the effects of the added damping ratio depend on the vibration mode. At an attack angle of 2° and a flow rate of 14 m/s, the natural frequency of the hydrofoil in the bending mode with leading edge cavitation increases up to 2.25% and the added damping ratio decreases by 9.00%, while the natural frequency in the torsional mode increases by 20.12% and the added damping ratio increases by 165.70%.

Key words

structural dynamics / leading edge cavitation / hydrofoil / natural frequency / added damping ratio

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YAO Zhifeng, LAI Guihua, LIU Jing, ZENG Yongshun. Numerical simulations of the effect of leading edge cavitation on the vibration characteristics of an elastic hydrofoil[J]. Journal of Tsinghua University(Science and Technology). 2021, 61(11): 1325-1333 https://doi.org/10.16511/j.cnki.qhdxxb.2020.22.043

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