Experimental research on impact effect of high speed water jet acting on a rigid target with attached water layer

Abstract

A well-characterized high speed water jet is ejected by explosion in a cylindrical cavity filled with water column, then the water jet impacts a rigid target covered by a section of attached water layer at the velocity up to 110 m/s. The evolution process and impact phenomenon of water jet are captured by a high speed camera while the impact load is recorded by a pressure sensor. The top shape of water jet is depended on the morphology of water column at cavity opening. The transient impact velocity and dimensions of water jet is obtained by post-processing of high speed camera pattern. When the water jet impacts the free surface of attached water layer with a flat shape, an air cushion appears between water jet and attached water. A transient compression wave generates at the impact interface. The compression wave propagates downwards and the pressure peak is captured by sensor. Due to second reflection of compression wave at the interface, a cavitation zone appears among the attached water layer. With the continues slamming of water jet at the rigid target, the impact load turns to steady hydrodynamic pressure. Both transient “water hummer” pressure and steady hydrodynamic pressure are discussed in detail. Then, the impact pattern and pressure of water jet acting on target plate covered by a section of attached water layer and rigid target directly with no attached water layer are compared. By controlling charge amount and thickness of attached water layer, the variation trends of impact velocity and impact load are presented.