Research Papers: Multiphase Flows

Cavitation Structures in a Venturi Flow With Various Backward Facing Steps

[+] Author and Article Information
Hailing An, Michael W. Plesniak

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907-2088

J. Fluids Eng 130(7), 071304 (Jun 26, 2008) (7 pages) doi:10.1115/1.2948370 History: Received September 06, 2007; Revised April 05, 2008; Published June 26, 2008

Cavitation inception and development caused by a backward facing step in a Venturi-type test section were studied experimentally for different step heights (0.84mm). High-speed cinematography and particle image velocimetry images were used to demonstrate the cloud shedding process and cavitation development stages. It was found that for small step height (0.8mm, hδ0=1.7) cavitation started in the reattachment region in the form of a reentrant jet, and caused cloud shedding in its developed stage. For high step height (4mm, hδ0=8.5) cavitation started midway downstream of the shear layer and resembled the spanwise vortices in the separated shear layer. This study contributes experimental results for better understanding of cavitation inception and development in the separated shear layer.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Schematic of the water loop and the test section

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Figure 2

Flow conditions of the incoming flow in test section: (a) axial velocity distribution and (b) turbulence intensity distribution

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Figure 3

PIV image processing example

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Figure 4

Pressure distribution for different step heights in Venturi test section

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Figure 5

Cavitation inception and development for baseline case. (a) Reh=8.8×103, σ=0.99; (b) Reh=9.2×103, σ=0.87; (c) Reh=9.4×103, σ=0.79; (d) Reh=9.9×103, σ=0.67; and (e) Reh=1.1×104, σ=0.47 (the step height h=0.8mm).

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Figure 6

Cloud cavitation shedding process for baseline case at σ=0.47. The major cavity is outlined with dashed line; cloud structures are labeled with circled numbers (the step height h=0.8mm).

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Figure 7

Selected PIV images of cavitation inception structures for 1.6mm step in Venturi test section at Reh=1.84×104, σ=1.07

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Figure 8

Selected PIV images of cavitation inception structures for 2.2mm step in Venturi test section at Reh=2.55×104, σ=1.14

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Figure 9

PIV images of cavitation structures in the shear layer of 4.0mm step in Venturi test section: (a) Reh=4.7×104, σ=1.33; (b) Reh=5.1×104, σ=1.12; (c) Reh=5.4×104, σ=0.99; and (d) Reh=5.8×104, σ=0.85

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Figure 10

Noncavitating vorticiy (Ωzh∕U0) field with separation bubble and cavitation zone marked: (a) h=0.8mm, (b) h=1.6mm, (c) h=2.2mm, and (d) h=4.0mm



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