NUMERICAL SIMULATION OF CRATER FORMATION HEATING BY LASER BEAM

Abstract

The numerical simulation of the transient heating and ablation of a two-dimensional axisymmetric target by a laser beam are presented. The numerical solution involves an implicit finite-difference method, with a three-level stepping scheme, which takes into account the nonlinearity of boundary conditions (heat radiation), and the temperature dependence of specific heat and anisotropic thermal conductivity. The coordinate transformation introduced by Landau for the one-dimensional problem is extended to the axisymmetric one. This transformation is used to immobilize and to straighten the complex moving boundary. To reduce computation time, a modified strongly implicit procedure (MSIP) is used to solve the linear system of algebraic equations. For validation, the numerical method was compared with an available analytical solution (heating of an orthotopic half-space by a Gaussian flux) and experimental configurations (ablation of an isotropic cylinder). It is shown that the heating of the semi-infinite target and the burn-through time of the cylinder are in good agreement with the analytical solution and the experimental process, in spite of the simplified radiation model used for the crater.