Research Papers: Multiphase Flows

Frequency in Shedding/Discharging Cavitation Clouds Determined by Visualization of a Submerged Cavitating Jet

[+] Author and Article Information
Ezddin A. F. Hutli, Milos S. Nedeljkovic

Faculty of Mechanical Engineering, University of Belgrade, Belgrade 11120, Serbia

J. Fluids Eng 130(2), 021304 (Jan 31, 2008) (8 pages) doi:10.1115/1.2813125 History: Received September 23, 2006; Revised July 11, 2007; Published January 31, 2008

Visualization of a highly submerged cavitating water jet was done by high-speed camera photography in order to study and understand the jet structure and the behavior of cloud cavitation within time and space. The influencing parameters, such as injection pressure, nozzle diameter and geometry, and nozzle direction (convergent and divergent), were experimentally proven to be very significant. Periodical shedding and discharging of cavitation clouds have been also analyzed and the corresponding frequency was determined by cloud shape analysis. Additionally, the dependence of this frequency on injection pressure and nozzle geometry has been analyzed and a simple formula of correspondence has been proposed. The formula has been tested on self-measured and literature data. The recordings of sonoluminescence phenomenon proved the bubble collapse everywhere along the jet.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Nozzle geometry (mm). From left to right: nozzle geometry, nozzle holder, ways of nozzle installation.

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Figure 2

(Left) Schematic diagram of a cavitating jet machine. (1) plunger pump, (2) filter, (3) regulation valve, (4) temperature sensor, (5) high-pressure transducer, (6) test chamber, (7) valve, (8) low-pressure transducer, (9) safety valve, (10) tank, (11) circulation pump, (12) heat exchanger, (13) energy destroyer in the bypass, and (14) pressure gauge. (Right) the test chamber.

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Figure 3

(Left-up) Visualization system, (Left-down) cavitating jet striking the specimen, and (Right) group of jet images obtained under the following conditions: convergent nozzle (Dout=0.45mm). P1=105bars, P2=2.06bars, VJ=124m∕s, σ=0.02568, T=18.5°C, X∕d=57.044. Camera: FASTCAM-APX 120K, frame rate: 50,000fps, shutter frequency: 1∕250,000s, resolution: 256×64, number of pictures in a film: 300 frames.

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Figure 4

(Left-two columns) Conditions: P1=105bars, P2=2.06bars, VJ=124m∕s, σ=0.02568, T=18.5°C. (Right-two columns) Conditions: P1=177bars, P2=2.06bars, VJ=162m∕s, σ=0.0155, T=18.5°C. Convergent nozzle. X∕d=57.044, frame rate: 24,000fps, shutter frequency: 1∕250,000s, resolution 512×128, and number of frames in a film: 300 frames.

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Figure 5

(Left-two columns) Conditions: P1=90.5bars, P2=1.89bars, VJ=18.2m∕s, σ=1.142, T=20°C. (Right-two columns) Conditions: P1=267bars, P2=1.89bars, VJ=31.5m∕s, σ=0.37, T=20°C. Divergent nozzle. X∕d=25.67, frame rate: 24,000fps, shutter frequency: 1∕250,000s, resolution: 512×128, and number of frames in a film: 300 frames.

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Figure 6

The variation of cloud cavitation length (Lc) with upstream pressure and nozzle geometry. S is shedding, D is discharging. (Left) authors’ data: (Right) data from Refs. 1,6.

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Figure 7

Cavitating water jet cloud width (Wc) behavior at different values of x∕d; (Left) convergent nozzle; (Right) divergent nozzle

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Figure 8

The first three diagrams represent cavitating water jet cloud width (Wc) behavior at different values of x∕d for convergent nozzle at injection pressure P1=105bars. The fourth diagram represents the cloud length (Lc) change with the time (measured along the center of the jet). The pattern is a sine wave for all and with the same frequency.

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Figure 9

An attempt to observe the luminescence phenomenon in a cavitating jet. The flow from left to right. Conditions: P1=213bars, VJ=191m∕s, T=22°C (σ=0.0125, σ=0.0142, and σ=0.0207 starting from left to right).



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