Visualization of the Early Stages of Shock Waves Generated with Silver-Azide Pellets by Laser Ignition Methods

Abstract

This paper describes the feature of shock waves generated by micro-charges, silver-azide, in the early stage of propagation. Silver-azide pellets (10 mg, cylindrical shape) were ignited with pulsed laser. Direction-indicating color schlieren method, schlieren method and double-exposure holographic interferometry were employed for visualization. Four different types of ignition method were examined to make the effects on the shock waves clear. In all the cases of ignition method, silver-azide pellets provided distorted spherical shock waves. The distorted portion on the shock waves, however, disappeared with propagation in the air. The propagation distance to transform to perfect spherical shock waves was estimated to be 120 mm. Additional experiments with reducing the weight of silver-azide to 0.5 mg was carried out to make it clear that a micro-charge with irregular shape would generate perfect spherical shock wave. The results from numerical simulation done with AUODYN-2D indicated that existence of directional combustion jet along the cylindrical axis was the major reason why the generated shock waves were distorted. Silver-azide, Micro-charges, Direction-indicating color schlieren method, Spherical shock waves, AUTODYN-2D * 2002 4 24 CRC