In this paper, a coupled thermal-fluid-structure numerical model is presented to investigate interactive effects of supersonic airflow, high power laser and metallic target. The numerical model is validated by experiments recently carried out by Lawrence Livermore National Laboratory. The numerical simulation also verified some experimental observations, which show that the convective heat transfer effects of airflow and the aerodynamic pressure play important roles to the damage behavior of laser irradiated target. The convective heat transfer of airflow reduces the temperature of laser irradiated area therefore delays the time reaching damage. When a thin-walled metallic panel is heated up to a high temperature below the melting point, it is softened and the strength nearly vanishes, the aerodynamic pressure becomes a dominant factor that controls the damage pattern even when it is in a low magnitude. The effects of airflow velocity and laser power on the damage behavior of irradiated metallic target are investigated with the aid of the coupled thermal-fluid-structure numerical model, where critical irradiation times to reach the yield failure t _yield and melting failure t _yield are the main concern. Results show that, when the incidence laser power increases from 500 W/cm² to 5000 W/cm², significant drop in failure times are found as the incidence laser power increases. When the Mach number of airflow increases from 1.2 to 4.0 at a given incident laser power, a critical airflow velocity is found for the irradiation time to reach the yield strength and melting point, i.e., the maximum irradiation time to reach failure is found at the Mach 1.8~2.0. The competition of aerodynamic heating before the laser is switch on and airflow cooling after the target is heated up accounts for effects.

Date Published: 16 May 2013
PDF: 7 pages
Proc. SPIE 8796, 2nd International Symposium on Laser Interaction with Matter (LIMIS 2012), 879605 (16 May 2013); doi: 10.1117/12.2010236

Published in SPIE Proceedings Vol. 8796:
2nd International Symposium on Laser Interaction with Matter (LIMIS 2012)
Stefan Kaierle; Jingru Liu; Jianlin Cao, Editor(s)