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Research Papers: Flows in Complex Systems

Numerical Analysis of Three Types of Cavitation Surge in Cascade

[+] Author and Article Information
Yuka Iga

Kei Hashizume

 Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan

Yoshiki Yoshida

 Kakuda Space Center, Japan Aerospace Exploration Agency (JAXA), 1 Koganezawa, Kimigaya, Kakuda, Miyagi 981-1525, Japan

J. Fluids Eng 133(7), 071102 (Jul 05, 2011) (13 pages) doi:10.1115/1.4003663 History: Received July 21, 2010; Revised February 07, 2011; Published July 05, 2011; Online July 05, 2011

In the present study, numerical analysis of a cavitating three-blade cyclic flat-plate cascade was performed considering cavitation surge, which is a type of cavitation instability in pumping machinery. A numerical method employing a uniquely developed gas-liquid two-phase model was applied to solve the unsteady cavitating flow field, where compressibility is considered in the liquid phase of the model. From the numerical results, the surging oscillations by cavitation represented in the present cascade system can be classified into three types of cavitation surge based on the oscillation characteristics and the flow fields. In the first type, oscillation is composed of small-vortex cavitation and large scale pulsation, which correspond to “surge mode oscillation” whose frequency is not affected by cavity volume. The second type of oscillation is composed of sheet cavitation with a re-entrant jet, which corresponds to so-called “cavitation surge.” The final type of oscillation is subsynchronous rotating cavitation accompanied by pulsation, which is considered as superposition of system and local instability. In addition, the locking phenomenon of break-off frequency of cavitation in the surging oscillations and the mechanism of the pulsation phenomenon accompanied by re-entrant jet in the present cascade were investigated.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of the three-blade cyclic flat-plate cascade of the present study (C/h=2.0,γ=75deg)

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Figure 2

Time-averaged cascade head of the present three-blade cyclic cascade and occurrence of cavitation instabilities

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Figure 3

Occurrence map of cavitation instabilities of the present three-blade cyclic cascade

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Figure 4

Waveforms of the variation of the cavity volume, the upstream pressure, and the mass flow rate under the condition without cavitation instabilities (φ=0.176, σ=0.343, and ψ=0.175)

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Figure 5

Waveforms of the variation of the cavity volume, the upstream pressure, and the mass flow rate under the condition of super-S. R.C (φ=0.105, σ=0.256, and ψ=0.167)

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Figure 6

Waveforms of the variation of the cavity volume, the upstream pressure, and the mass flow rate under the condition of R-stall C. (φ=0.0699, σ=0.0791, and ψ=0.125)

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Figure 7

Waveforms of the variation of the cavity volume, the upstream pressure, and the mass flow rate under the condition of type 1 C.S. (φ=0.0699, σ=0.624, and ψ=0.160)

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Figure 8

Waveforms of the variation of the cavity volume, the upstream pressure, and the mass flow rate under the condition of type 2 C.S. (φ=0.105, σ=0.162, and ψ=0.186)

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Figure 9

Waveforms of the variation of the cavity volume, the upstream pressure, and the mass flow rate under the condition of type 3 C.S. (φ=0.0699, σ=0.296, and ψ=0.142)

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Figure 10

Power spectra of the waveforms of the cavity volume variation on a blade in each cavitation instabilities

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Figure 11

Power spectra of the waveforms of the upstream pressure in each cavitation instabilities

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Figure 12

Time evolution of the void fraction distribution under the condition of type 1 C.S. (φ=0.0699, σ=0.624, and ψ=0.160; time interval=3.2ms)

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Figure 13

Time evolution of the pressure distribution under the condition of type 1 C.S. (φ=0.0699, σ=0.624, and ψ=0.160; time interval=3.2ms)

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Figure 14

Time evolution of the void fraction distribution under the condition of type 2 C.S. (φ=0.105, ψ=0.162, and ψ=0.186; time interval=2.0ms)

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Figure 15

Time evolution of the pressure distribution under the condition of type 2 C.S. (φ=0.105, σ=0.162, and ψ=0.186; time interval=2.0ms)

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Figure 16

Time evolution of void fraction distribution under condition of type 3 C.S. (φ=0.0699, σ=0.296, and ψ=0.142)

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Figure 17

Time evolution of the pressure distribution under the condition of type 3 C.S. (φ=0.0699, σ=0.296, and ψ=0.142)

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Figure 18

Frequency of cavity break-off cycle in the one-blade cyclic cascade (C/h=2.0,γ=75deg)

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Figure 19

Strouhal number of cavity break-off cycle in the one-blade cyclic cascade (C/h=2.0,γ=75deg)

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Figure 20

Surging frequency occurring in three types of cavitation surge in the three-blade cyclic cascade

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Figure 21

Strouhal number of cavity break-off occurring in three types of cavitation surge in the three-blade cyclic cascade

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Figure 22

Time evolution of the pressure distribution on a blade and the extended line under the condition of type 2 C.S. (φ=0.105, σ=0.162, and ψ=0.186)

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Figure 23

Time evolution of the mass flux vectors around the sheet cavitation of type 2 C.S. (φ=0.105, σ=0.162, and ψ=0.186)

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Figure 24

Time evolution of the velocity vectors and pressure in the vicinity of the leading edge under the condition of cavitation surge (φ=0.105, σ=0.162, and ψ=0.186)

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