The influence of structural deformation on water jet impact loading

The collapse of an underwater explosion bubble near a solid structure is accompanied by the formation of a high-speed re-entrant liquid jet. The intensity of this jet and the pressure loading generated on the body are functions of the characteristics of both the explosion bubble and the structure. The dynamics of the structure and the bubble are fully coupled. Boundary motions can modify the bubble dynamics and re-entering jet characteristics. The structure response also modifies the jet loading due to jet impact. To study the modification of the jet impact loading due to the structural response, a series of simple, well-controlled experiments were conducted. Water jets of known characteristics were impacted on plates of varying flexibility and their response and the pressure loads measured. Substantial reduction in peak load is seen due to the presence of plate flexibility. Similar results were obtained using our bubble dynamics code, 2DYNAFS, coupled to a structural dynamics code, NIKE2D, to study the coupled response of a deformable interacting structure and a nearby bubble. Results of both the experimental and numerical studies highlight the need for utilizing fully coupled calculations of explosion bubble loading on structures. (C) 1998 Academic Press Limited.