Direct simulation of the high temperature optical behaviour of a porous medium based on a CT image

A numerical method based on ray tracing is proposed to reproduce the thermal radiative properties of random heterogeneous media constituting of scatterers (voids, pores, particles, grains, fibers) with typical sizes largely superior to the considered wavelength. This method requires the thorough knowledge of both the texture of the medium and the complex optical indexes of the solid phases constituting it. The term texture refers here to the spatial arrangement of the scatterers (pores, voids, grains, fibers) inside the host matrix and also to their respective size distributions. The texture is retrieved by analysing an X-ray computed μ-tomographic image of the sample. This method is applied to a fused silica glass containing gaseous bubbles. The comparison between the calculated normal emittance spectrum and the experimental spectrum acquired on the porous glass at T = 1300 K by high temperature infrared emittance spectroscopy, allowed to test the validity of the approach.