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Research Papers: Multiphase Flows

An Experiment for the Study of Free-Flying Supercavitating Projectiles

[+] Author and Article Information
Peter J. K. Cameron

G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332peterjkcameron@gatech.edu

Peter H. Rogers, John W. Doane, David H. Gifford

G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332

J. Fluids Eng 133(2), 021303 (Mar 02, 2011) (9 pages) doi:10.1115/1.4003560 History: Received April 01, 2010; Revised February 02, 2011; Published March 02, 2011; Online March 02, 2011

Applications and research utilizing supercavitation for high-speed underwater flight has motivated study of the phenomenon. In this work, a small scale laboratory experiment for studying supercavitating projectiles has been designed, built, and tested. Similar existing experimental work has been documented in literature but using large, elaborate facilities, or has been presented with ambiguous conclusions from test results. The projectiles were 63.5 mm in length and traveled at speeds on the order of 145 m/s. Measurement techniques are discussed and used to record projectile speed, supercavity dimensions, and target impact location. Experimental observations are compared with a six degrees-of-freedom dynamics simulation based on theoretical models presented in literature for predicting supercavity shape and hydrodynamic forces on the supercavitating projectile during flight. Experimental observations are discussed qualitatively, along with quantitative statistics of the measurements made. Successful operation of the experiment has been demonstrated and verified by agreement with theoretical models.

FIGURES IN THIS ARTICLE
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Copyright © 2011 by American Society of Mechanical Engineers
Topics: Projectiles , Cavities
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Figures

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Figure 1

Schematic showing experiment setup including camera viewing positions and induction coil locations

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Figure 2

Projectile photographs: (left, side view, and middle) looking down at the projectile tips showing the disk cavitators and (right) projectile tail showing embedded magnet discussed in Sec. 2. Projectile dimensions are length=63.58±0.05 mm, tip diameter=2.92±0.01 mm, and tail diameter=11.49±0.06mm (measured statistics with a measurement uncertainty of 0.01 mm).

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Figure 3

Example of recorded induction coil data (for physical locations of coil sets 1–3, see Fig. 1)

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Figure 4

Forces on a supercavitating projectile during tail-slap

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Figure 5

Side view images from high-speed digital photography of a supercavitating projectile. Camera viewing from the upper position in Fig. 1.

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Figure 6

Images from high-speed digital photography of a supercavitating projectile showing three images of the same shot with time increasing from left to right (t=0 ms, t=2.4 ms, and t=3.2 ms). The camera view is from the lower position in Fig. 1.

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Figure 7

Set of side view (upper camera position in Fig. 1) images showing cavity closure. Time increasing from left to right in 270 μs intervals.

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Figure 8

Plots of supercavity dimension against projectile speed. The error bars show estimated measurement precision (see Sec. 3).

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Figure 9

Left: projectile speed (vertical component of tail velocity) as a function of time. The solid lines represent predicted curves from the simulation run at evenly spaced (10 m/s increments) initial speeds. The circle markers show data points joined by dashed lines representing experiments with similar but not exactly corresponding initial speeds. Right: target impact locations (CEP=7.56 mm).

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