The present paper reports on an experimental study for underwater shock wave generation using high-pressure gas in order to trigger bubble motion in water. Shock waves are generated by an original diaphragmless shock tube. This shock tube produces a shock wave of Mach number 1.38 using an initial compressed air of 0.5 MPa in a driver section. A shock wave is discharged into an acrylic pipe provided with a silicone film. This acrylic pipe is set slightly above water surface. Excessive pressure and density increasing behind an incident shock wave have the silicone film rapidly deformed. Underwater shock waves are produced by impingement of a silicone film on water surface. Optical visualization is carried out using a high-speed camera, and a number of hemispherical underwater shock waves are observed with impact of the silicone film against the water surface. In addition, the impact velocity of the silicone film is considered to be over 20 m/s for generation of underwater shock waves.
