Effect Of Anisotropy On Radiative Transport In Random Media

Anisotropy inevitably exists in random media,in which radiation transport is more complex.The effect of anisotropy on radiation transport is still unclear.It is of great significance to study its radiative properties in environmental monitoring,medical imaging and remote sensing.In this study,the radiation transfer in anisotropic random media are analyzed in scalar and vector perspectives respectively.In the study of scalar radiation transfer,the QSGS algorithm is applied to construct porous microstructures with different pore shapes,pore sizes and porosities and the angular scattering intensity distribution is calculated by FDTD method.Later,absorption coefficient,scattering coefficient and asymmetry factor are retrieved simultaneously based on RTE by combining Monte Carlo method with Particle Swarm Optimization.We retrieve radiative properties of porous media based on numerically exact simulation,which is original and effective in solving light scattering by porous media.It avoids establishing complicated models and manufacturing samples with certain microstructural parameters,which are quite difficult and time-consuming.The simulation can be accurate enough so that it can be regarded as a virtual experiment,which takes anisotropic pore shape and wave effect into account.This method can also be applied to other porous media,which designs a frame work for further simulation study of porous media.Compared with spherical shape,irregular anisotropic pore shape reduces the forward scattering peak.The method used in this paper can also be applied to other porous media,which designs a frame work for further quantitative study on porous media.In the study of vector radiation transfer,we apply Monte Carlo simulation and DDA to study the mechanism of polarized radiation transfer in anisotropic random media.We investigated the effect of structural anisotropy and optical anisotropy and have found that the diagonal symmetry properties of the Mueller matrix of isotropic random medium are destroyed.The difference can be used to detect the existence of structural anisotropy and optical anisotropy.The depolarization rate of scattered light depends on the polarization state of incident light,the number of scattering times and the anisotropy of medium.Optical anisotropy can accelerate the depolarization rate of scattering light,while structural anisotropy has an opposite effect on depolarization of circularly polarized light and linearly polarized light.When structural anisotropy and optical anisotropy coexist,they may produce a cooperative effect on depolarization.