2025
Yin, Tingyun; Pavesi, Giorgio
Study of sheet cavitation on a pitching hydrofoil Proceedings Article
In: Journal of Physics: Conference Series, Institute of Physics, 2025, ISSN: 17426596.
Abstract | Links | BibTeX | Tags: Cavitation, Pitching Hydrofoil, Sheet Cavitation
@inproceedings{Yin2025,
title = {Study of sheet cavitation on a pitching hydrofoil},
author = {Tingyun Yin and Giorgio Pavesi},
doi = {10.1088/1742-6596/3143/1/012125},
issn = {17426596},
year = {2025},
date = {2025-01-01},
urldate = {2025-01-01},
booktitle = {Journal of Physics: Conference Series},
volume = {3143},
issue = {1},
publisher = {Institute of Physics},
abstract = {The dynamic cavitation on a moving wall is garnering increasing interest because many fluid machinery systems operate under dynamic conditions in real-world scenarios. This study adopts a numerical method to investigate sheet cavitation on a pitching hydrofoil with the objective of elucidating the dynamic behaviour of the cavity and its influence on hydraulic performance. The results show that dynamics of the sheet cavity on the up-pitching hydrofoil exhibit significant delay effects. Within the downstroke phase from the maximum to the mean angle of attack, the features of the sheet cavity on the pitching hydrofoil are close to those on the stationary hydrofoil. However, the swift pitching action of the hydrofoil can result in a rapid fluctuation in the second derivative of the cavity area. The hydrofoil consistently experiences a significant reduction in lift and an increase in drag.},
keywords = {Cavitation, Pitching Hydrofoil, Sheet Cavitation},
pubstate = {published},
tppubtype = {inproceedings}
}
The dynamic cavitation on a moving wall is garnering increasing interest because many fluid machinery systems operate under dynamic conditions in real-world scenarios. This study adopts a numerical method to investigate sheet cavitation on a pitching hydrofoil with the objective of elucidating the dynamic behaviour of the cavity and its influence on hydraulic performance. The results show that dynamics of the sheet cavity on the up-pitching hydrofoil exhibit significant delay effects. Within the downstroke phase from the maximum to the mean angle of attack, the features of the sheet cavity on the pitching hydrofoil are close to those on the stationary hydrofoil. However, the swift pitching action of the hydrofoil can result in a rapid fluctuation in the second derivative of the cavity area. The hydrofoil consistently experiences a significant reduction in lift and an increase in drag.
2022
Yin, Tingyun; Pavesi, Giorgio
Dynamic responses of pitching hydrofoil in laminar–turbulent transition regime Journal Article
In: Journal of Fluids and Structures, vol. 111, 2022, ISSN: 10958622.
Abstract | Links | BibTeX | Tags: Dynamic stall model, Laminar separation bubble, Laminar–turbulent transition, Pitching Hydrofoil
@article{YinPavesi2022-01,
title = {Dynamic responses of pitching hydrofoil in laminar–turbulent transition regime},
author = {Tingyun Yin and Giorgio Pavesi},
doi = {10.1016/j.jfluidstructs.2022.103544},
issn = {10958622},
year = {2022},
date = {2022-01-01},
journal = {Journal of Fluids and Structures},
volume = {111},
publisher = {Academic Press},
abstract = {Recently, the problem of a transitional boundary layer around a pitching foil has been attracting increasing attention. To determine the underlying physical mechanisms, in this study, a pitching hydrofoil is numerically investigated using the shear stress transport (SST) k–ω turbulence model coupled with the γ–Re˜θt transition model. First, the prediction of the static performance is compared with the experimental measurements and XFOIL data to validate and verify the numerical accuracy of the proposed method. Subsequently, the flow morphologies induced by sinusoidal and non-sinusoidal pitching laws are analyzed and compared in different reduced frequencies. The results indicate that reducing the empirical coefficient, A1, in the SST k–ω turbulence model can generate the flow separation in advance, thus improving the prediction of the hydraulic performance at a high angle of attack. The dynamic behavior of the laminar separation bubble is strongly associated with the pitching method and velocity. The collapse of the laminar separation bubble can destabilize the local boundary layer, generating multi-laminar separation bubbles. When new separation bubbles form and shed, a turbulent boundary layer moves downstream and is adsorbed on the surface simultaneously. The turbulence flow passes through the trailing edge, destroying the local vortex, contributing to a transiently elevated hydrodynamic lift. During a rapid pitching down, a counterclockwise trailing edge vortex becomes increasingly unstable, repeating the processes of inception, development, and shedding. The Theodorsen model fails to produce a reasonable hysteresis loop owing to the assumption of a fully attached flow. The results of a hybrid of the Theodorsen and Øye models show noticeable improvement in the dynamic lift prediction. The empirical coefficient, ks, of the Snel model is optimized, improving the predictions of low-frequency pitching significantly. All dynamic stall models present the same trend: low-frequency motions show better agreement than high-frequency ones. In the former, modeling of a non-sinusoidal pitching is closer to the transient numerical results than that of a sinusoidal motion.},
keywords = {Dynamic stall model, Laminar separation bubble, Laminar–turbulent transition, Pitching Hydrofoil},
pubstate = {published},
tppubtype = {article}
}
Recently, the problem of a transitional boundary layer around a pitching foil has been attracting increasing attention. To determine the underlying physical mechanisms, in this study, a pitching hydrofoil is numerically investigated using the shear stress transport (SST) k–ω turbulence model coupled with the γ–Re˜θt transition model. First, the prediction of the static performance is compared with the experimental measurements and XFOIL data to validate and verify the numerical accuracy of the proposed method. Subsequently, the flow morphologies induced by sinusoidal and non-sinusoidal pitching laws are analyzed and compared in different reduced frequencies. The results indicate that reducing the empirical coefficient, A1, in the SST k–ω turbulence model can generate the flow separation in advance, thus improving the prediction of the hydraulic performance at a high angle of attack. The dynamic behavior of the laminar separation bubble is strongly associated with the pitching method and velocity. The collapse of the laminar separation bubble can destabilize the local boundary layer, generating multi-laminar separation bubbles. When new separation bubbles form and shed, a turbulent boundary layer moves downstream and is adsorbed on the surface simultaneously. The turbulence flow passes through the trailing edge, destroying the local vortex, contributing to a transiently elevated hydrodynamic lift. During a rapid pitching down, a counterclockwise trailing edge vortex becomes increasingly unstable, repeating the processes of inception, development, and shedding. The Theodorsen model fails to produce a reasonable hysteresis loop owing to the assumption of a fully attached flow. The results of a hybrid of the Theodorsen and Øye models show noticeable improvement in the dynamic lift prediction. The empirical coefficient, ks, of the Snel model is optimized, improving the predictions of low-frequency pitching significantly. All dynamic stall models present the same trend: low-frequency motions show better agreement than high-frequency ones. In the former, modeling of a non-sinusoidal pitching is closer to the transient numerical results than that of a sinusoidal motion.
