Numerical study of radiative properties of birds' feathers using Monte Carlo method

To investigate the radiative heat transfer in birds' coatings necessitates knowing the radiative properties such as absorption coefficient, scattering coefficient, and phase function. In the present work, by simulating an arrangement similar to the structure of the birds' feathers, the radiative properties were investigated using Monte Carlo method for fibers with diameters of 5, 10, 15, and 20 mu m at fiber volume fractions of 1%, 3%, 5%, and 7% and at different angles for fibers in two dark and light colors. According to the results, by increasing the fiber's diameter from 5 to 20 mu m, the attenuation coefficient was reduced by 75%. Considering the studied diameters, an increase in the fiber's volume fraction from 1% to 7% led to an increase of 531% in the average attenuation coefficient. In fibers with light color, by increasing the fiber's diameter from 5 to 20 mu m, the average albedo (the scattering coefficient-to-attenuation coefficient ratio) at volume fractions of 1%, 3%, 5%, and 7% was reduced by 10%, 12%, 13%, and 14%, respectively. Considering the studied diameters in the light-colored fibers, increasing the fiber's volume fraction from 1% to 7% led to a reduction of 12% in the average albedo. However, in the dark-colored fibers, the albedo showed slight changes. As indicated by the results, although the average attenuation coefficient was independent of the fibers' arrangement, the changes in the arrangement of the fibers significantly affected the angular distribution of the attenuation coefficient.