各向异性对随机多孔涂层辐射特性的影响研究

Effect of Anisotropy on Thermal Radiation Transport in Porous Ceramics

本文基于对空气等离子喷涂(APS)多孔热障涂层的实际微观结构的分析,首次研究了其辐射特性的各向异性性质。建立了考虑涂层中非球形孔隙及其朝向分布的微结构模型,采用离散偶极子算法(DDA)求解了该多孔微结构在不同辐射热流传输方向的辐射特性分布。为了精确研究微纳结构辐射特性的各向异性对宏观热流传输的影响,本文提出了一种各向异性随机行走方法,推导了相应的宏观传输特性参数,并与传统基于各项同性介质的结果进行了对比。结论表明,涂层辐射特性的各向异性对涂层辐射热流传输有一定影响,实际计算与设计中必须加以考虑。

In this study, we numerically demonstrate the anisotropy of radiative properties of the air plasma sprayed （APS） TBC for the first time based on its microstructures. The anisotropic microstructures of APS TBCs are quantitatively reconstructed containing nonspherical pores with various orientations, in which the anisotropic mesoscopic radiative properties are computed using the discrete dipole approximation （DDA）. To fully depict the effect of anisotropy on radiative transfer in a macroscopic scale, a random walk scheme is thus proposed to solve the anisotropic radiative transfer problem in such medium, and the macroscopic transport mean free path is derived. We show that anisotropy of radiative properties affects the transmitted radiative heat flux across it considerably, which should be taken into account in practical calculations and design.