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Fundamental Issues and Canonical Flows

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

[+] Author and Article Information
Xianwu Luo

State Key Laboratory of Hydroscience and Engineering,  Tsinghua University, Beijing, 100084, P. R. C.luoxw@mail.tsinghua.edu.cn

Bin Ji1

State Key Laboratory of Hydroscience and Engineering,  Tsinghua University, Beijing, 100084, P. R. C.jibin@mail.tsinghua.edu.cn

Xiaoxing Peng

 China Ship Scientific Research Center, Wuxi, 214082, P. R. C.

Hongyuan Xu

State Key Laboratory of Hydroscience and Engineering,  Tsinghua University, Beijing, 100084, P. R. C.

Michihiro Nishi

Senior Academy,  Kyushu Institute of Technology, Kitakyushu, 804-8550, Japan

1

Corresponding author.

J. Fluids Eng 134(4), 041202 (Apr 20, 2012) (10 pages) doi:10.1115/1.4006416 History: Received March 09, 2011; Revised December 09, 2011; Published April 19, 2012; Online April 20, 2012

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.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic diagram of evaporation and condensation

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Figure 2

Test twisted hydrofoil: (a) The section profile of hydrofoil, (b) Span-wise distribution of angle of attack, (c) A bird’s-eye view

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Figure 3

Pressure coefficient distributions at different profile sections of twisted hydrofoil in non-cavitation condition

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Figure 4

Computation domain and boundaries

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Figure 5

Time averaged lift and drag coefficients against mesh number

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Figure 6

Mesh generation around hydrofoil surface

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Figure 7

Locations of a high speed video system and lamps: (a) Cross-sectional view of test section, (b) Side view of test section

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Figure 8

A sketch of camera viewing area

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Figure 9

Cavitation pattern during a cycle of cavity shedding: numerical bird’s-eye view (left), numerical top view (middle), experimental top view (right). (a) t = T/6, (b) t = 2T/6, (c) t = 3T/6, (d) t = 4T/6, (e) t = 5T/6, (f) t = 6T/6.

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Figure 10

Velocity vector fields just before the primary cavity shedding (t = 2T/6 + 7T/60)

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Figure 11

Strouhal number (St=fl/V∞) as a function of cavitation number

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Figure 12

Evolution of cavity shedding and re-entrant jet formation near the rear region of the hydrofoil: (a) t = 5T/6, (b) t = 5T/6 + 4T/60, (c) t = 5T/6 + 8T/60, (d) t = 5T/6 + 12T/60, (e) t = 5T/6 + 16T/60, and (f) t = 5T/6 + 20T/60

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Figure 13

Observation of side-entrant jets by a HSV system (sampling frequency: 4k Hz)

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Figure 14

Instantaneous velocity vector field over the suction surface of hydrofoil: (a) t = 5T/6, (b) t = 6T/6

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Figure 17

Pressure coefficients distribution along the chord of the mid-span at different instants

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Figure 19

Wall-pressure fluctuations at the position of x/C = 0.1

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Figure 18

Wall-pressure fluctuations in the chord-wise direction: (a) z/C = 1.71, (b) z/C = 1.51, (c) z/C = 1.31

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Figure 16

Lift and drag fluctuations: (a) Lift coefficient, (b) Drag coefficient

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Figure 15

Instantaneous streamline distribution at t = 2/6T

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