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The implosion of cylindrical shell structures in a high-pressure water environment
C M Ikeda1, J Wilkerling1, J H Duncan1
1Department of Mechanical Engineering , University of Maryland , College Park, MD 20742, USA.
Proceedings. Mathematical, Physical, and Engineering Sciences
|December 20, 2013
Summary
Experiments show that cylindrical shell implosions in water generate pressure waves. Wave characteristics depend on shell geometry and initial pressure, with larger length-to-diameter ratios favoring simpler implosion modes.
Area of Science:
- Experimental fluid dynamics
- Structural mechanics
- Acoustics
Background:
- Cylindrical shell structures are susceptible to catastrophic implosion under external hydrostatic pressure.
- Understanding the dynamics of underwater implosions is crucial for naval engineering and offshore structure design.
- Previous studies have explored buckling and collapse, but detailed analysis of pressure wave generation during implosion is ongoing.
Purpose of the Study:
- To experimentally investigate the implosion of thin-walled cylindrical shells in a high-pressure water environment.
- To characterize the generated pressure waves and their scaling with key physical parameters.
- To determine the influence of structural geometry, specifically the length-to-diameter ratio, on implosion modes and wave characteristics.
Main Methods:
- Thin-walled aluminium and brass cylindrical shells, sealed with internal air, were subjected to controlled implosion in a high-pressure water tank.
- Implosion events were captured using high-speed digital movie cameras.
- Simultaneous measurement of pressure waves was performed using an array of underwater blast sensors.
Main Results:
- For larger length-to-diameter ratios (L/D0), shells flattened into a two-lobe (mode 2) shape, with pressure waves scaling primarily with critical pressure (Pc) and a characteristic time scale.
- For smaller L/D0 ratios, higher-mode cross-sectional shapes were observed during implosion.
- Pressure signal amplitudes and shapes were significantly influenced by the mode number of implosion, although temporal scaling remained consistent.
Conclusions:
- The length-to-diameter ratio is a critical parameter governing the mode of cylindrical shell implosion.
- Pressure wave characteristics are primarily dictated by the critical implosion pressure and water properties for simple modes.
- Higher-order implosion modes lead to more complex pressure wave signatures, highlighting the importance of mode number in predicting acoustic emissions.
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