An investigation into container constraint effects on the cavity characteristics due to high-speed projectile water entry

Abstract

In this paper, the influence of container dimension constraints on the cavity expansion characteristics were preliminary investigated through series of high-speed water-entry experiments with velocity in the range of 80–470 m/s. Particular attention is given to the characteristics of cavity evolution, surface and deep closure, average cavity wall velocity and the drag coefficient under container constraints. In the test configurations, three size cylindrical-shaped containers were employed, a digital high-speed camera system is used to photograph the projectile motion and cavity expansion within the water-filled containers. Experimental results show that the cavity in a larger container will reach a larger radius and collapses later than the cavity in a much smaller container. The container size has little effect on the time of surface closure and the location of deep closure but more on the time of deep closure. Moreover, it is found that as the container size decreases to a magnitude of the cavity diameter, the projectile velocity attenuation will be strongly affected by the container constraint. The objective of the present study is to provide original dynamic data for studying the nature of hydrodynamic ram caused by the cavity expansion in subsequent work.