Models of concentrated energy flux effects on homogeneous and porous media

Physical and mathematical models of the processes accompanying the effect of strong radiation fluxes on homogeneous (metals) and porous media are described. For a homogeneous medium, the model describes the processes of heating and evaporation of the surface, unsteady-state axisymmetric expansion of vapors into the surrounding space and the motion thus induced of air displaced from the surface. At the absorbed energy flux densities of up to 100 W/sq cm, the processes of transport of the directly emitted thermal radiation of vapors and air plasma become essential which lead, in particular, to additional heating and evaporation of the surface outside the region of primary radiation absorption. Calculations are carried out for the case of aluminum and bismuth surface irradiation by a neodymium laser operating in regular and irregular modes. For porous materials the characteristic feature is the formation of a volumetric heat source. The procedures for the description of radiation absorption in two models (capillary and globular) of porous media with an opaque skeleton are presented. Specific features of temperature fields in a porous plate exposed to constant and pulse-periodic radiation fluxes are discussed.