Study of dynamic underwater implosion mechanics using digital image correlation

The physical processes associated with the implosion of cylindrical tubes in a hydrostatic underwater environment were investigated using high-speed three-dimensional digital image correlation (3D DIC). This study emphasizes visualization and understanding of the real-time deformation of the implodable volume and the associated fluid-structure interaction phenomena. Aluminium 6061-T6 cylindrical tubes were used as the implodable volumes. Dynamic tourmaline pressure transducers were placed at selected locations to capture the pressure history generated during each implosion event. A series of small-scale calibration experiments were first performed to establish the applicability of 3D DIC for measuring the deformation of submerged objects. The results of these experiments indicated that the effects of refraction due to water and the optical windows can be accounted for by evaluation of the camera's intrinsic and extrinsic parameters using a submerged calibration grid when the surface normal of the optical windows is collinear with the camera's optical axis. Each pressure history was synchronized with its respective high-speed DIC measurements. DIC results showed that the highest rate of increase in contact area correlates to the largest pressure spike during the implosion process. The results also indicated that, for a given diameter, longer implodable volumes generated higher pressure spikes.