Approach to Radiative Heat Transfer in Infrared-active Gas Including Scattering Particles through a Direct Solution Method of the Maxwell's Electro-Magnetic Equation

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Scattering pattern of radiative energy scattered by particles varies with number density of particles. At the first stage of increase in number density, the intensity of scattered energy drops in the range of small scattering angle. But, the decline of scattered energy does not appear in the range of large scattering angle. In the next stage of increase in number density, the decline of scattered energy becomes remarkable in the rage of small scattering angle, and the region of fall down in scattering intensity becomes wide toward the range of large scattering angle. When the decline of scattering intensity reaches to the edge of diffraction region, the decline of scattering intensity can be recognized over the whole range of scattering angle. When the number density of scattering objects becomes much higher, scattering intensity goes down remarkably over the whole range of scattering angle. This means that the phase function based on the scattering pattern formed by a single particle … More can not be used when the number density of scattering particles are very high and the influence of multiple-scattering effect is storing. As for the number density of scattering particles, the effect of multiple scattering disappears more quickly when the distances among particles is widened in the direction of optical axis than when widened in the direction perpendicular to the optical axis. In the latter case, the critical distances among scattering angle where the multiple-scattering effect disappears is clarified.On condition that the effect of multiple scattering can be neglected, the influence of particle shape was examined by inverting the scattering pattern formed by plural scattering objects of same shape existing in arbitrary posture into particle size distribution. When the length of scattering objects is extended keeping the diameter, the mean diameter and variance of size distribution of equivalent spheres become large. But, the longer becomes the particle, variation in the mean diameter and variance becomes more moderate. When the shape of particles is rotating ellipsoid, the variance of size distribution is very small and the mean diameter obtained from the inversion of scattering pattern is equivalent to the diameter of a circle having same area as the average of projected shapes formed by the particle of arbitrary posture.Direct finite difference solution method of the electro-magnetic equation can predict the electromagnetic field among scattering particles though the Mie's scattering theory cannot predict it. On the other hand, the external product of electric field E and magnetic field H means the vector compound of energy flux in all direction. Therefore, it was not clarified how to know the radiative intensity from the electro-magnetic field obtained from the finite difference solution method. This problem was solved in this investigation. Less