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Research Papers

Implosion of Longitudinally Off-Centered Cylindrical Volumes in a Confining Environment

[+] Author and Article Information
Sachin Gupta

Dynamic Photo Mechanics Laboratory,
Department of Mechanical,
Industrial and Systems Engineering,
University of Rhode Island,
Kingston, RI 02881
e-mail: gupsac@my.uri.edu

James M. LeBlanc

Naval Undersea Warfare Center
(Division Newport),
Newport, RI 02841
e-mail: james.m.leblanc@navy.mil

Arun Shukla

Fellow ASME
Dynamic Photo Mechanics Laboratory,
Department of Mechanical,
Industrial and Systems Engineering,
University of Rhode Island,
Kingston, RI 02881
e-mail: shuklaa@uri.edu

1Corresponding author.

Manuscript received December 9, 2014; final manuscript received February 24, 2015; published online March 12, 2015. Editor: Yonggang Huang. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Appl. Mech 82(5), 051002 (May 01, 2015) (12 pages) Paper No: JAM-14-1573; doi: 10.1115/1.4029917 History: Received December 09, 2014; Revised February 24, 2015; Online March 12, 2015

A comprehensive experimental/numerical study on the implosion of longitudinally off-centered cylindrical implodable volumes was conducted within a tubular confining space. In particular, the aim of this study was to examine the changes in the implosion mechanics and in the nature of pressure waves, arising from the longitudinally off-centered location of the implodable volume. Experiments were conducted with 31.8 mm outer diameter, cylindrical aluminum 6061-T6 implodable volumes placed concentrically within the confining tube. Three longitudinal offset locations were chosen within the confining tube, such that distance from the center of the implodable volume to the center of confining tube is equal to: (a) zero, (b) 3/7 of the half-length of confining tube (L), and (c) 5 L/7. Pressure transducers mounted on the inner surface of the confining tube were used to capture the pressure waves released during the implosion event. Computational simulations were performed using a coupled Eulerian–Lagrangian scheme to explicitly model the implosion process of the tubes along with the resulting compressible fluid flow. The experiments revealed that the longitudinal asymmetric placement of the implodable volume enhances the strength of hammer pressure waves generated during the implosion process. The off-centered location of the implodable volume causes a pressure imbalance in the entire length of the confining tube. Hence, the water particle velocity shifts toward the implodable volume producing high pressure region at the end-plate near the implodable volume, while the other end-plate experiences significantly longer cavitation due to low pressure. This far end-plate cavitation duration is also found to increase with increasing longitudinal offset, even though the total combined cavitation duration at both the end-plates is approximately same for all offset locations. With high correlation observed between the experiments and simulations, computation models were further used to correlate the longitudinal offset and the signature of pressure waves at various interpolated locations. Simulations show that there is increase in both the peak pressure and the impulse of the hammer wave with increasing longitudinal offset of the implodable volume. Simulations also show that the collapse rate of the implodable volume decreases with the increasing longitudinal offset.

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References

Figures

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Fig. 4

Fluid model of air inside the implodable volume, high pressure water inside the confining tube and initial entrapped air bubble for centrally placed implodable volume

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Fig. 3

Structural model of the confining tube and implodable volume (5L/7 offset shown)

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Fig. 2

Schematic of the implodable volume with end-caps and support collets

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Fig. 1

Schematic of the experiment setup. Distance between the center of the confining tube and the center of the implodable volume equals to (a) zero, (b) 3L/7, and (c) 5L/7. The full length of the confining tube, 2L = 2.286 m.

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Fig. 5

Pressure history inside the confining tube for implodable volume placed at the center (a) left half confining tube and (b) right half confining tube

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Fig. 6

Pressure spatial distribution inside the confining tube for implodable volume placed at the center

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Fig. 7

Pressure history inside the confining tube for implodable volume placed at an offset of 5L/7

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Fig. 8

Pressure spatial distribution inside the confining tube for implodable volume placed at an offset of 5L/7

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Fig. 9

Schematic of similarity between a symmetrically and highly asymmetrically placed implodable volume within a confining tube

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Fig. 10

Uniaxial water particle velocity generated inside the confining tube for the case of (a) centrally placed, (b) 3L/7 away from center, and (c) 5L/7 away from center. The size of the arrow shown in this figure is proportional to the magnitude of longitudinal particle velocity of water at that location.

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Fig. 14

Pressure history inside the confining tube for implodable volume placed at an offset of 3L/7

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Fig. 15

Pressure spatial distribution inside the confining tube for implodable volume placed at an offset of 3L/7

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Fig. 11

Pressure history correlation between experiments and simulations for the case of (a) centrally placed, (b) 3L/7 away from center, and (c) 5L/7 away from center

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Fig. 12

(a) Pressure history at the near end-plate from simulations for varying offset locations. (b) Pressure–impulse observed at the end-plate as a function of offset location.

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Fig. 13

(a) Center-point velocity of the implodable volume for all offset locations. (b) Change in the internal volume of the implodable for all offset locations.

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