Holographic interferometric visualization of weak shock waves in castor oil packed with equal-diameter gelatine spheres

Abstract

The attenuation of shock waves in castor oil in which equal-diameter gelatine spheres were packed was measured with hydrophones at various stand-off distances. The motion of shock waves was quantitatively visualized by using double exposure holographic interferometry. Diameters of gelatine spheres under study were 3.0 mm ±1%, 4.5 mm ±1%, and 6.0 mm ±1%. Shock waves were produced at the center of a chamber in which gelatine spheres of total 4 L in volume were densely immersed in castor oil. In order to generate shock waves, irradiation of a pulsed YAG laser beam on silver azide pellets were used. The weight of silver azide pellets ranged from 3 μg to 10 mg, with their corresponding energy of 4.5 mJ to 15 J. The effect of the nonuniformity on the shock-wave attenuation created due to the multiple interaction of shock waves with the gelatine spheres was experimentally clarified. The result will be useful to establish a model of human tissue in numerically simulating the complex interaction of underwater shock waves with human tissue which takes place in shock-wave therapies.