Investigation of shock wave focusing in water in a logarithmic spiral duct, Part 2: Strong coupling

Underwater explosions near submerged marine structures can lead to severe conditions and subsequent damage, particularly if the geometry of the solid structure leads to shock focusing of the incident shock wave. In order to understand the dynamic response of submerged marine structures subjected to underwater explosions it is important to understand the fluid-structure coupling that occurs during the shock focusing event. In this paper, experiments and numerical simulations of shock focusing in thin water-filled convergent structures are conducted to study the fluid-structure interaction and the dynamic response of the surrounding structure. Three types of materials have been investigated: 1018 steel, 6061 aluminum and a 16-layer carbon-fiber-reinforced epoxy composite. Two different thicknesses of the steel and aluminum specimens have been used: 1.3 mm and 5.8 mm. The carbon fiber specimen was 5.8 mm thick, with the same weight as the 1.3 mm thick steel specimen. Results show that the type of material, its geometry, and its thickness play a substantial role in determining the fluid-structure interaction during and after the shock focusing event.