Interaction of a planar shock wave with a water surface

This work is about experimental study of a planar shock wave which slide over a water surface. The aim is to observe the air-water interface and the droplet entrainment which is associated. Experiments are performed at atmospheric pressure in a 200×200-mm²-square-cross-section shock tube for depths of 10, 20 and 30 mm and two incident planar shock waves having Mach number of 1.11 and 1.43. We recorded the pressure histories and high-speed visualization to study the flow patterns, surface waves and spray layers behind the shock wave. We observed two different flow patterns with ripples formed at the air-water interface for the weaker shock wave and the dispersion of a droplet mist for the stronger shock wave. We analyzed pressure signals both in the air and in the water at the same location. From these pressure signals we extracted the delay time between the arrival of the compression wave into the water and the shock wave in air at the same location. We show that the delay time evolves with the distance traveled over the water layer, the depth of the water layer and the Mach number of the incident shock wave.