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TECHNICAL PAPERS

Thermal Cavitation Experiments on a NACA 0015 Hydrofoil

[+] Author and Article Information
Angelo Cervone

 Alta S.p.A., Via Gherardesca 5, 56121 Pisa, Italya.cervone@alta-space.com

Cristina Bramanti, Emilio Rapposelli

 Alta S.p.A., Via Gherardesca 5, 56121 Pisa, Italy

Luca d’Agostino

Department of Aerospace Engineering, University of Pisa, Via G. Caruso, 56100 Pisa, Italy

J. Fluids Eng 128(2), 326-331 (Sep 13, 2005) (6 pages) doi:10.1115/1.2169808 History: Received August 02, 2004; Revised September 13, 2005

The present paper illustrates the main results of an experimental campaign conducted in the Thermal Cavitation Tunnel of the Cavitating Pump Rotordynamic Test Facility (CPRTF) at Centrospazio/Alta S.p.A. Experiments were carried out on a NACA 0015 hydrofoil at various incidence angles, cavitation numbers, and freestream temperatures, in order to investigate the characteristics of cavitation instabilities and the impact of thermal cavitation effects. Measured cavity length, surface pressure coefficients, and unsteady pressure spectra are in good agreement with the data available in the open literature and suggest the existence of a strong correlation between the onset of the various forms of cavitation and instabilities, the thermal cavitation effects, and the effects induced by the presence of the walls of the tunnel. Further analytical investigations are planned in order to provide a better interpretation of the above results.

Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

CPRTF with the pump test section (left) and the Thermal Cavitation Tunnel mounted on the suction line

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Figure 2

Schematic of the test section with the NACA 0015 hydrofoil and the locations of the pressure taps on the hydrofoil surface (x), at the section inlet (o) and outlet (o)

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Figure 3

Pressure coefficient on the suction side of the NACA 0015 hydrofoil in noncavitating conditions for various incidence angles α at room water temperature. CFD simulation at 8deg incidence angle and room water temperature (solid line). Experimental uncertainty in the evaluation of the pressure coefficient is about 1.5% of the nominal value.

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Figure 4

Influence of thermal cavitation effects on surface pressure distribution on the NACA 0015 hydrofoil at constant angle of attack α and cavitation number σ for several water temperatures T. Experimental uncertainty in the evaluation of the pressure coefficient is about 2% of the nominal value.

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Figure 5

Normalized maximum and minimum lengths of the cavity as function of the cavitation number σ for various incidence angles α at room water temperature. Experimental uncertainty in the evaluation of the cavity length is about 4% of the chord length.

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Figure 6

Characteristics of cavity length at 8deg incidence angle and room water temperature. Experimental uncertainty in the evaluation of the cavity length is about 4% of the chord length.

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Figure 7

Frequency spectrum of the upstream pressure at 8deg incidence angle and room water temperature

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Figure 8

Typical cavitation appearance in “bubble+cloud” case (α=4deg,σ=1.25,T=25°C)

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Figure 9

L.E., maximum and minimum lengths of the cavity for three different water temperatures T at 8deg incidence angle. Experimental uncertainty in the evaluation of the cavity length is about 4% of the chord length.

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Figure 10

Frequency spectrum of the upstream pressure at 8deg incidence angle and 50°C water temperature

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Figure 11

Frequency spectrum of the upstream pressure at 8deg incidence angle and 70°C water temperature

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Figure 12

Cavity thickness for three different water temperatures T at the same incidence angle α and cavitation number σ(α=8deg,σ=2.5)

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Figure 13

Cavitation appearance at higher freestream temperature (α=8deg,σ=2,T=70°C)

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Figure 14

Normalized pressure drop caused by the hydrofoil for various incidence angles α at room water temperature. Experimental uncertainty in the evaluation of the pressure drop is about 5% of the nominal value.

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Figure 15

Normalized pressure drop caused by the hydrofoil for three different water temperatures T at 8deg incidence angle. Experimental uncertainty in the evaluation of the pressure drop is about 5% of the nominal value.

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