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Research Papers: Multiphase Flows

Large Eddy Simulation of Unsteady Cavitating Flow Around a Highly Skewed Propeller in Nonuniform Wake

[+] Author and Article Information
Chao Yu, Xiaocui Wu, Tezhuan Du

Key Laboratory for Mechanics in Fluid
Solid Coupling Systems,
Institute of Mechanics,
Beijing 100190, China

Yiwei Wang

Key Laboratory for Mechanics in Fluid
Solid Coupling Systems,
Institute of Mechanics,
School of Engineering Science,
University of Chinese Academy of Sciences,
Beijing 100190, China
e-mail: wangyw@imech.ac.cn

Chenguang Huang

Key Laboratory for Mechanics in Fluid
Solid Coupling Systems,
Institute of Mechanics,
School of Engineering Science,
University of Chinese Academy of Sciences,
Beijing 100190, China

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received December 2, 2015; final manuscript received October 26, 2016; published online February 15, 2017. Assoc. Editor: Elias Balaras.

J. Fluids Eng 139(4), 041302 (Feb 15, 2017) (10 pages) Paper No: FE-15-1881; doi: 10.1115/1.4035218 History: Received December 02, 2015; Revised October 26, 2016

Abstract

Unsteady cavitating flows around propellers become increasingly prominent on large-scale and high-speed ships, but large eddy simulations (LES) are limited in the literature. In this study, numerical simulation of an unsteady cavitating flow around a highly skewed propeller in a nonuniform wake is performed based on an explicit LES approach with $k−μ$ subgrid model. Kunz cavitation model, volume of fluid (VOF) method, and a moving mesh scheme are adopted. The predicted evolution of the unsteady cavitating flow around a highly skewed propeller in a nonuniform ship wake is in good agreement with experimental results. An analysis of the factors affecting the cavitation on the propeller is conducted based on numerical simulation. Furthermore, the influences between cavitation structures and vortex structures are also briefly analyzed.

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Figures

Fig. 1

Propeller geometry

Fig. 2

Measured nominal wake distribution (Wx=1−vx/V∞) [19]

Fig. 3

Computation domain

Fig. 4

Wake distribution at 0.3 D before the propeller plane

Fig. 5

Pressure distribution at 0.3 D before the propeller plane

Fig. 6

Details of the element layout: (a) is the section of X = 0 and (c) is the section of Z = 0.3 D

Fig. 7

Evolution of the cavity pattern during propeller rotation. (Numerical results are in the first and third row, while experimental results are in the next row.)

Fig. 8

Variations of thrust coefficient and torque coefficient in numerical results. (The thrust coefficient is presented by the black line with the left label, while the torque coefficient is presented by the blue line with the right label.)

Fig. 9

The distributions of Cp on the section of blade at 0.9 R. (b0.9R is the chord of blade at 0.9 R,Cp=(p−p∞)/(0.5ρn2D2) is pressure coefficient.)

Fig. 10

Fig. 11

Variations of cavity shape on cylindrical section 0.9 R

Fig. 12

Influencing factors of the cavity on cylindrical sections. (The relative flow velocity v is composed of the relative rotational linear velocity vτp=2πnr, where r is the distance to rotation axis, the wake flow velocity which mainly includes tangential velocity vτ and the axial velocity vx. The attack angle α is an angle between the relative flow velocity and the section of the blade and α=β−γ, where β is the pitch angle of the blade and γ is the angle between the tangential direction and relative flow velocity.)

Fig. 13

Variations of axial velocity vx and tangential velocity vτ comparing with the area of cavity on section 0.9 R. (The axial velocity is presented by the black line with the left label, the tangential velocity is presented by the red line with the center label, and the cavity area is presented by the blue line with the right label. The axial velocity and tangential velocity are captured from the point on the plane 0.3D before the propeller plane corresponding to the center point on the chord.)

Fig. 14

Variations of the local cavitation index (σt) and the attack angle (α) comparing with the cavity area (A) on section 0.9 R. (The local cavitation index is presented by the black line with the left label, the attack angle is presented by the red line with the center label, and the cavity area is presented by the blue line with the right label).

Fig. 15

The wake flow axial velocity distribution and cavity (X = −0.15 D)

Fig. 16

Cavity region on circle d = 0.9 D (ψ1,ψ2 are the cavity region in the left and right on circle d = 0.9 D, respectively)

Fig. 17

The wake flow tangential velocity distribution (X = −0.15 D)

Fig. 18

Vortex structures (Q = 500,000 s−2)

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