Identification of microscale heat transfer parameters using bioinspired algorithms

The paper is devoted to an identification of microscale heat transfer parameters. The numerical modeling of short-pulse laser interaction with thin metal films is considered. The hyperbolic two-temperature model describing the temporal and spatial evolution of the lattice and electrons temperatures in the irradiated metal is applied. This model consists of four equations: two equations concern the electron and lattice temperatures, the remaining equations determine the dependencies between heat fluxes and temperatures. The short-pulse laser interaction with the film is taken into account by introduction of internal volumetric heat source to the equation describing the electrons temperature. The equations concerning the electrons and lattice temperatures are joined by the coupling factor G which characterizes the energy exchange between phonons and electrons. The relations between electrons heat flux and electrons temperature and between lattice heat flux and lattice temperature contain the parameters te and tl, respectively. Parameter te is the relaxation time of free electrons in metals, parameter tl is the relaxation time in phonon collisions. The 1D problem is analyzed (heat transfer in the direction perpendicular to the thin film is taken into account). At the front surface irradiated by a laser pulse and the back surface the non-flux conditions can be accepted. The initial conditions are also assumed. The direct problem is solved by explicit scheme of finite difference method. The results of computations are partially compared with the experimental data available in literature. The inverse problem discussed here consists in the simultaneous identification of three parameters, namely coupling factor G and relaxation times te and tl. To solve such problem the electrons temperature history at the irradiated surface of thin film is taken into account. The bioinspired algorithm are used in optimization process. In the final part of the paper the results of computations are shown and the conclusions are formulated.