Transient radiative transfer in two graded-index slab adhered by an infinitely thin vacuum via the lattice Boltzmann method

The lattice Boltzmann method is presented to solve the radiative transport of both diffuse and collimated problems in inhomogeneous and semitransparent two - layered slab with graded refractive indices. The two layers are bounded by Fresnel's walls and separated by an infinitely thin vacuum interlayer with neg-ligible thickness to represent the case with surface roughness or assembling of two layers using a trans-parent binder or intumescent resin. The high - order discrete ordinates is used to simulate the angular redistribution due to variable refractive indices and multiple reflections at the boundaries and interface. The accuracy and efficiency of the methodology is firstly tested for transient and steady state solution in two - layered slab with constant or variable refractive indices. Effects of the distributions of refractive indices and surrounding, scattering albedos, and the optical thicknesses on the transient radiative signals are examined. Calculation results show that, these parameters have a significant influence on radiative transfer and the angular intensities at different few times levels are presented to illustrate the effects of the interface characteristics, and the discontinuous nature of the intensity at the interface is discussed. The developed LBM is a promising, efficient and simple solver to perform the radiative transport in inho-mogeneous layered media with graded - index functions. (c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

The lattice Boltzmann method is used to solve the radiative transport in inhomogeneous and semitransparent two-layered slabs. The method accurately simulates the angular redistribution and multiple reflections at the boundaries and interface. The effects of refractive indices, scattering albedos, and optical thicknesses on the transient radiative signals are examined.