Study of diverging and converging spherical shock waves induced by micro explosives in an aspherical transparent test section

摘要

The paper reports an experimental study of production and propagation of diverging and converging spherical shock waves. In order to quantitatively observe spherical shock waves and the flow field behind them, an aspheric spherical transparent test section was designed and constructed. This 150 mm inner-diameter aspheric lens shaped test section permits the collimated visualization laser light beam to traverse the test section parallel and emerge parallel. Spherical diverging shock waves were produced at the center of the spherical test section. In order to generate shock waves, irradiation of a pulsed Nd:YAG laser beam on micro silver azide pellets were used. The weight of silver azide pellets ranged from 1 to 10 mg, with their corresponding energy of 2.1 to 21 J. Pressure histories at different points over the test section were measured to validate production of uniform shock waves. After reflection of spherical shock wave from the test section, a converging spherical shock wave was produced. Double exposure holographic interferometry and time resolved high speed photography were used for flow visualization. The whole sequence of diverging and converging spherical shock waves propagation and their interaction with product gases were studied.