Abstract: With local thermodynamic equilibrium approximation,radial position-dependent energy flux for diffusive supersonic wave in low density filled cylinder or sphere shell structures with high density walls are given. We obtain arched-type distribution of geometric factor versus radius in cylinder and sphere shell structure. Mean geometric factor is obtained from cross-section average of total radiative energy flux. Effect of spherical shell structure on radiation process is much greaterr than that of cylinder structure. Geometrical free path must be considered in simulation of radiative diffusivity or thermal conductivity for sphere shell structures models. A fitted formula of geometric factor according to numerical solutions is given.

Key words: radiative diffusion, radiative energy flux, geometric factor, geometrical free path