免费论文：各向异性散射梯度反射率介质内辐射传播接洽

Developing methods for anisotropic scattering radiative transfer in graded index medium and investigating effects of graded index and anisotropic scattering on radiative transfer within the medium are going to be a new forefront. In anisotropic scattering medium and graded index medium, propagating directions of radiative energy are both changed. Affected by anisotropic scattering and graded index, radiative energy distributions in spatial directions are inhomogeneous. In this thesis, to solve anisotropic scattering radiative transfer which traditional ray-tracing method can hardly deal with in multidimensional medium, the curved ray-tracing method is proposed for radiative transfer in one-dimensional and multidimensional anisotropic scattering, especially nonlinear scattering medium with homogeneous and graded refractive index.The main content of the thesis is as follows:1. Analytical curved ray-tracing method is applied to solve radiative transfer in linear scattering medium with black boundary and graded index. According to theoretic analysis, radiative transfer in the medium with linear refractive index distributions is related to the ratio, rather than the difference of refractive index in two boundaries. Effects of optical thickness, the scattering albedo, asymmetry factor of scattering phase function, dimensionless refractive index gradient on radiative transfer are investigated. 2. The equivalence of Analytical curved ray-tracing method and the pseudo-source adding method is proved.To solve linear scattering radiative transfer in one-dimensional graded index medium with diffuse gray boundary, analytical curved ray-tracing method and the pseudo-source adding method are adopted. It is proved by formulation derivation that two methods are equivalent. Effects of various combinations of graded index and boundary emissivities on the temperature and dimensionless radiative heat flux distributions are also investigated.3. The integral moment method is presented to solve nonlinear scattering radiative transfer in one-dimensional homogeneous and graded refractive index medium.In the integral moment method for one-dimensional case, only spatial coordinate is discretized, while solid angle is integrated directly. Thus, ray effects are avoided. The integral moment method has a good convergence characteristic according to the influence of grid number on computational results. When discretizing space, two methods are considerded, inner node integral coefficient method and outer node composite Simpson quadrature method. Computational results of two methods are compared in cases of different grid number. Effects of graded index and anisotropic scattering on radiative transfer are investigated. This thesis presents the spherical harmonics method for radiative transfer in nonlinear scattering and graded index medium and compares results of the spherical harmonics method with that of the integral moment method.4. The pseudo-source adding method is developed to solve nonscattering radiative transfer in graded index medium with diffuse gray boundary.The discrete number of solid angle plays an important role in algorithmic stability when the medium has a larger absorption coefficient and a reasonable explanation is presented. This thesis discusses influences of graded index on the temperature field in the medium and pseudo-source temperature of boundaries and studies the temperature field in inhomogeneous absorption coefficient medium.5. The integral moment method is applied to solve nonlinear scattering radiative transfer in two-dimensional homogeneous and graded refractive index medium. This thesis solves anisotropic scattering radiative transfer in two-dimensional graded index medium by the combination of the integral moment method and discrete curved ray-tracing method. Results are compared with that of references and show that this method is good in accuracy. Furthmore, Effects of graded index on anisotropic scattering radiative transfer are investigated and changes of temperature and radiative heat flux fields in the medium with different graded index distributions are analyzed.

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