Date of Award
Doctor of Philosophy (PhD)
A fundamental experimental investigation was conducted to understand the underwater dynamic implosion of cylindrical metallic shells. In particular, the attention was focused on studying the generation of pressure waves from implosion in varying confining situations such that the fluid structure interaction with the confined structures governs the mechanics of implosion process. The experiments were conducted in three environments: (a) free-field environment represented by a large underwater pressure vessel facility, (b) partially closed environment represented by one-end open confining tube, (c) completely closed environment represented by closed confining tube. This study also utilizes the visualization and understanding of the realtime deformation of the implodable volumes using high speed 3-D Digital Image Correlation (DIC) technique. This technique was modified and recalibrated for each environment to accurately capture the full-field underwater deformations and velocities of the collapsing implodable volume. Dynamic tourmaline pressure transducers along with face pressure transducers were used in the experiments to capture the near field pressure history during the implosion event. Both structural DIC measurements and pressure signatures were synchronized for understanding the fluid structure interaction process. The free-field experiments were conducted with varying length to diameter ratio implodable volumes to study the basic implosion mechanics in the absence of confining structures. Two separate implosion studies were conducted in one-end open confining tube. First study was aimed to understand the general physics of water hammer wave evolution in the open-ended confining tube in conjunction with DIC measurements. Second study addresses the problem of sympathetic implosion of adjacently placed structures in the confining tube. Four studies were conducted in completely closed confined environment. First study evaluates the mechanics of implosion occurring inside a closed confining tube with centrally placed implodable volumes. It also looks to understand the effect of increasing size of the implodable volume on the confined implosion mechanics. Second study was conducted to examine the changes in implosion mechanics due to longitudinal offset location of the implodable volume. Third study extends the first study by performing real time high speed DIC measurements to correlate the evolution of implosion waves with implodable volume’s deformations. This also investigates the effect of trapped air bubble inside the closed confining on the rate/extent of collapse in implodable volume. Fourth study was conducted to understand the shock initiated implosion mechanics inside the confining tube with DIC measurements.
Gupta, Sachin, "UNDERWATER IMPLOSION OF CYLINDRICAL METALLIC SHELLS IN CONFINING ENVIRONMENTS" (2015). Open Access Dissertations. Paper 326.