NUMERICAL INVESTIGATION OF UNSTEADY CAVITATING FLOW ON A THREE-DIMENSIONAL TWISTED HYDROFOIL

Abstract This study employs an incompressible homogeneous flow framework with a transport-equation-based cavitation model and shear stress transport turbulence model to successfully reproduce the unsteady cavitating flow around a three-dimensional hydrofoil. Cavity growth, development, and break-off during the periodic shedding process are adequately reproduced and match experimental observations. The predicted shedding frequency is very close to the experimental value of 23 ms. By monitoring the motions of the seeding trackers, growth-up of attached cavity and dynamic evolution of U-type cavity are clearly displayed, which indicating the trackers could serve as an effective tool to visualize the cavitating field. Repelling Lagrangian Coherent Structure (RLCS) is so complex that abundant flow patterns are highlighted, reflecting the intricacy of cavity development. The formation of cloud cavities is clearly characterized by the Attracting Lagrangian Coherent Structure (ALCS), where bumbling wave wrapping the whole shedding cavities indicates the rotating transform of cavities and stretching of the wave eyes shows the distortion of vortices. Generation of the re-entrant jet is considered to be not only associated with the adverse pressure gradient due to the positive attack angle, but also the contribution of cloud cavitating flow, based on the observation of a buffer zone between the attached and cloud cavities.

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Effects of Wavy Leading-Edge Protuberance on Hydrofoil Performance and Its Flow Mechanism

Journal of Marine Science and Engineering ◽

10.3390/jmse9101138 ◽

2021 ◽

Vol 9 (10) ◽

pp. 1138

Author(s):

Jing Li ◽

Chunbao Liu ◽

Xiaoying Li

Keyword(s):

Flow Instability ◽

Three Dimensional ◽

Leading Edge ◽

Streamwise Vortex ◽

Cavitating Flow ◽

Cavitation Inception ◽

Vortex Interactions ◽

Cavitation Pressure ◽

Les Model ◽

Unsteady Cavitating Flow

This paper examines the effects on a Clark-y three-dimensional hydrofoil of wavy leading-edge protuberances in a quantitative and qualitative way. The simulation is accompanied by a hybrid RANS-LES model in conjunction with Zwart-Gerber–Belamri model. Detailed discussions of the stable no-cavitating, unsteady cavitating flow fields and the control mechanics are involved. The force characteristics, complicated flow behaviors, cavitation–streamwise vortex interactions, and the cavitating flow instability are all presented. The results demonstrate that protuberances acting as vortex generators produce a continuous influx of boundary-layer vorticity, significantly enhancing the momentum transfer of streamwise vortices and therefore improving the hydrodynamics of the hydrofoil. Significant interactions are described, including the encouragement impact of cavitation evolution on the fragmentation of streamwise vorticities as well as the compartmentation effect of streamwise vorticities binding the cavitation inception inside the troughs. The variations in cavitation pressure are mainly due to the acceleration in steam volume. In summary, it is vital for new hydrofoils or propeller designs to understand in depth the effects of leading-edge protuberances on flow control.

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Numerical investigation of unsteady cavitating turbulent flows around a three-dimensional hydrofoil using stress-blended eddy simulation

Proceedings of the Institution of Mechanical Engineers Part E Journal of Process Mechanical Engineering ◽

10.1177/09544089211025119 ◽

2021 ◽

pp. 095440892110251

Author(s):

Jing Li ◽

Chunbao Liu ◽

Zilin Ran ◽

Bosen Chai

Keyword(s):

Numerical Investigation ◽

Turbulent Flows ◽

Large Scale ◽

Flow Instability ◽

Cavity Growth ◽

Hybrid Approach ◽

Three Dimensional ◽

Cavitating Flow ◽

Rans Model ◽

Eddy Simulation

The mechanism of flow instability, which involves complex gas–liquid interactions and multiscale vortical structures, is one of the hot research areas in cavitating flow. The role of turbulence modeling is crucial in the numerical investigation of unsteady flow characteristics. Although large-eddy simulation (LES) has been used as a reliable numerical method, it is computationally costly. In this work, we used a hybrid Reynolds-averaged Navier–Stokes (RANS) and LES model, that is, stress-blended eddy simulation (SBES), to improve the prediction capability for the cloud cavitating flow. Our hybrid approach introduces a shielding function to integrate the RANS model with the LES applied only regionally, such as to large-scale separated flow regions. The results showed that the periodic shedding of cavity growth, break off, and collapse around a three-dimensional Clark-Y hydrofoil was reproduced in accordance with experimental observations. The lift/drag coefficients, streamwise velocity profiles, and cavity patterns obtained by the SBES model were in better agreement with the experimental data than those obtained by the modified RANS model. The re-entrant jet dynamics responsible for the break off of the attached cavity were discussed. Further analysis of vorticity transportation indicated that the stretching and dilatation terms dominated the development of vorticity around the hydrofoil. In conclusion, the SBES model can be used to predict cavitating turbulent flows in practical engineering applications.

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Numerical investigation of three-dimensional cavitation evolution and excited pressure fluctuations around a twisted hydrofoil

Journal of Mechanical Science and Technology ◽

10.1007/s12206-014-0622-4 ◽

2014 ◽

Vol 28 (7) ◽

pp. 2659-2668 ◽

Cited By ~ 13

Author(s):

Bin Ji ◽

Xianwu Luo ◽

Yulin Wu ◽

Kazuyoshi Miyagawa

Keyword(s):

Numerical Investigation ◽

Pressure Fluctuations ◽

Three Dimensional ◽

Twisted Hydrofoil

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Numerical Simulation of Cavity Shedding from a Three-Dimensional Twisted Hydrofoil and Induced Pressure Fluctuation by Large-Eddy Simulation

Journal of Fluids Engineering ◽

10.1115/1.4006416 ◽

2012 ◽

Vol 134 (4) ◽

Cited By ~ 46

Author(s):

Xianwu Luo ◽

Bin Ji ◽

Xiaoxing Peng ◽

Hongyuan Xu ◽

Michihiro Nishi

Keyword(s):

Large Eddy Simulation ◽

Pressure Fluctuation ◽

Three Dimensional ◽

Cavitating Flow ◽

Numerical Results ◽

Central Plane ◽

Eddy Simulation ◽

Large Eddy ◽

Cavity Shedding ◽

Twisted Hydrofoil

Simulation of cavity shedding around a three-dimensional twisted hydrofoil has been conducted by large eddy simulation coupling with a mass transfer cavitation model based on the Rayleigh-Plesset equation. From comparison of the numerical results with experimental observations, e.g., cavity shedding evolution, it is validated that the unsteady cavitating flow around a twisted hydrofoil is reasonably simulated by the proposed method. Numerical results clearly reproduce the cavity shedding process, such as cavity development, breaking-off and collapsing in the downstream. Regarding vapor shedding in the cavitating flow around three-dimensional foils, it is primarily attributed to the effect of the re-entrant flow consisting of a re-entrant jet and a pair of side-entrant jets. Formation of the re-entrant jet in the rear part of an attached cavity is affected by collapse of the last shedding vapor. Numerical results also show that the cavity shedding causes the surface pressure fluctuation of the hydrofoil and the force vibration. Accompanying the cavity evolution, the wave of pressure fluctuation propagates in two directions, namely, from the leading edge of the foil to the trailing edge and from the central plane to the side of the hydrofoil along the span. It is seen that the large pressure fluctuation occurs at the central part of the hydrofoil, where the flow incidence is larger.

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