An experimental and numerical study of laser-induced spark in air

The present work studied the expansion of a laser-induced spark in air. The experiments were carried out using the beam deflection technique. Numerical analysis used a simple one-dimensional spherical model and the governing equations were integrated numerically using the MacCormack predictor-corrector scheme. The present results indicated that the shock radius R is proportional to shock arrival time t0.4 and the shock pressure is proportional to R−3 as functionally described by the blast wave theory. For the range of the spark energies from 15 to 50 mJ, the shock front reached a distance of about 2 mm within a few microseconds or less. During this period the shock-wave energy loss was from about 51% to 70%, the radiation energy losses accounted for were from 22% to 34%, and the energy of the remaining hot gas, was about 7-8% of the absorbed energy.