Dynamic characteristics of underwater objects after shock wave loading

This work focuses on the motion of underwater solid objects after shock wave loading, which is the fundamental phenomenon of various applications such as cleaning, defragmentation and sterilization. Particle Image Velocimetry (PIV) as a fluid measurement technique has been utilized widely. However, when applied to shock wave in water, its accuracy remains questionable because of the short interaction time. So that, in this study, the motions of objects made of three materials, copper, aluminum and PMMA, after shock loading were quantified experimentally. The sequential shadowgraph images of the object motions were recorded using a high-speed camera, and the displacement and then the velocity were obtained from the image analysis. The motion of object was numerically simulated, and its pressure was also obtained from numerical simulation. It is found that the initial velocity and peak pressure differs significantly from the materials of the object, and the velocity of objects made of different materials is not inversely proportional to its density. This observation strongly suggests that the velocity of a solid object, e.g. the tracer particle in PIV, after shock wave loading is resulted from the dynamic interaction between the ambient fluid and the object, in addition to the fluid force that has been commonly analyzed.