Energy balance of plume flow field for nanosecond laser ablation Al

To study the instant flow process induced by high power pulsed laser ablation Al and energy change process of the plume flow field, the plume expansion and its evolution process were researched by shadowgraph technique. The sequence diagrams of the ablation plume evolution were obtained. The model of the laser ablation plume expanding in ambient gas was set up based on the momentum equation. According to the experimental results, the energy balance process among the kinetic energy of the plume, the kinetic energy of the background gas and the thermal energy of the plume and background gas in dimensionless units were analyzed. Results show that, at early times pressure gradients drive the ablation plume expansion as if it were expanding in vacuum, then the kinetic energy of the plume is gradually dissipated into kinetic and thermal energy of the background gas. The dimensionless kinetic energy of the plume is almost equal to the kinetic energy of the gas and the thermal energy is nearly equal to the half of the total energy when the dimensionless shock wave radius is 1. Eventually, the energy converts into the thermal energy of the plume and background gas. ©, 2015, Journal of Propulsion Technology. All right reserved.