偏振对辐射传递计算精度的影响

Effects of polarization on numerical accuracy of radiative transfer

偏振是散射光的重要特征之一，而标量辐射传输方程中不包含有偏振信息。当考虑散射光的偏振或者是有高精度要求时，需用矢量辐射传输方程。利用求解矢量辐射传输方程的双层迭代解法，针对两种均匀介质中单色偏振辐射传输的一维平行平板模型，分析了偏振对辐射强度和热流计算结果的影响。计算结果表明，若不考虑偏振，在反照率较大、光学薄、有镜反射表面的一维介质中辐射强度的最大相对误差可以达到10％左右；在反照率较大、光学厚、有平行光源入射的一维介质中辐射强度的最大相对误差可以达到6％～7％左右。而不考虑偏振时对热流的计算结果的影响并不大。

Polarization is one of the most important characteristics of the scattering light, but the scalar radiative transfer equation does not include the polarization information. However, if the polarization of the scattering light or the high accuracy of numerical simulation is considered, the vector radiative transfer equation need to be solved. In this paper, the doubling-adding method was adopted to solve the vector radiative transfer equation. Two different plane-parallel and vertically-homogeneous mediums were taken as examples to analyze the numerical error due to omitting light polarization. The numerical result indicates that in the medium with large albedo, small optical depth and a specular reflective surface, the maximal relative error of radiative intensity could reach as much as 10%, while in the medium with large albedo, large optical depth and parallel solar irradiation, the maximal relative error of radiative intensity could reach 6%- 7%. However, there is just a little influence on numerical results of heat flux.