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Research Papers: Multiphase Flows

# Hydrofoil Cavitation Under Strong Thermodynamic Effect

[+] Author and Article Information
Jonas P. Gustavsson

Department of Mechanical and Aerospace Engineering, University of Florida, P.O. Box 116250, Gainesville, FL 32611jgu@ufl.edu

Kyle C. Denning, Corin Segal

Department of Mechanical and Aerospace Engineering, University of Florida, P.O. Box 116250, Gainesville, FL 32611

J. Fluids Eng 130(9), 091303 (Aug 12, 2008) (5 pages) doi:10.1115/1.2953297 History: Received August 29, 2007; Revised May 08, 2008; Published August 12, 2008

## Abstract

Cavitation was studied for a NACA0015 hydrofoil using a material that simulates cryogenic behavior. Several angles of attack and flow speeds up to $8.6m∕s$ were tested. The material used, 2-trifluoromethyl-1,1,1,2,4,4,5,5,5-nonafluoro-3-pentanone, hereafter referred to as fluoroketone, exhibits a strong thermodynamic effect even under ambient conditions. Static pressures were measured at seven chordwise locations along the centerline of the hydrofoil suction side and on the test section wall immediately upstream of the hydrofoil. Frequency analysis of the test section static pressure showed that the amplitude of the oscillations increased as the tunnel speed increased. A gradual transition corresponding to the Type II-I sheet cavitation transition observed in water was found to occur near $σ∕2α=5$ with Strouhal numbers based on chord dropping from 0.5 to 0.1 as the cavitation number was reduced. Flash-exposure high-speed imaging showed the cavity covering a larger portion of the chord for a given cavitation number than in cold water. The bubbles appeared significantly smaller in the current study and the pressure data showed increasing rather than constant static pressure in the downstream direction in the cavitating region, in line with observations made in literature for other geometries with fluids exhibiting strong thermodynamic effect.

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## Figures

Figure 1

Water tunnel test facility

Figure 2

Suction side pressure coefficient at different freestream speeds (left) and energy spectra at the test section static tap (right) at various freestream flow speeds in m∕s; α=4deg, σ=2.92 at 5.2m∕s, σ=2.14 at 6.7m∕s, and σ=1.67 at 8.6m∕s

Figure 3

Suction side pressure coefficient at different freestream speeds (left) and energy spectra at the test section static tap (right) at various freestream flow speeds in m∕s; α=6.6deg, σ=2.80 at 5.2m∕s, σ=2.00 at 6.7m∕s, and σ=1.54 at 8.6m∕s

Figure 4

Suction side pressure coefficient at different freestream speeds (left) and energy spectra at the test section static tap (right) at various freestream flow speeds in m∕s; α=8deg, σ=1.53 at 5.2m∕s, σ=1.21 at 6.7m∕s, and σ=1.06 at 8.6m∕s

Figure 5

Vapor formation on suction side of NACA0015 hydrofoil captured at 1270fps at 5.2m∕s, 8deg angle of attack at σ=1.53. Flow from left to right, leading edge at horizontal pixel 146, trailing edge at 773, scale: 81μm∕pixel.

Figure 6

Strouhal number of dominant frequency based on hydrofoil chord length plotted versus angle of attack-corrected cavitation number for several water studies. The three types of oscillatory behavior suggested by Arndt (11) are indicated by Roman numerals. Conditions for tests where significant oscillations were seen in fluoroketone are indicated by x.

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