Abstract:
A study was made of the physical properties of the so-called foam – a low-density (the average density is ~1 μg cm-3) microstructured medium. Foams of different type were classified according to the specific features of their internal structure. The propagation of high-power laser radiation through these media was considered and the relationships for the depth of radiation penetration for differently structured foams were obtained. Based on a self-similar solution describing the expansion of a film (filament) with its simultaneous heating by the law T = Atα, a model of the heat propagation through a porous medium was proposed and a relationship for the hydrothermal wave velocity νht=[4K/α(α+2)]1/2cT was obtained (cT is the isothermal sound velocity in the bulk of the heated material and K is a constant determined in the context of the model). The hydrothermal wave velocity was shown to be substantially determined by the processes occurring on a foam microstructure scale. The velocity dependence on the parameters of these processes was analysed within the framework of the proposed model.
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