Faithin Omaha eBook Collection

Download or read book Brownian Diffusion of Submicron Particles in Air Under Nonequilibrium Conditions written by W. George N. Slinn and published by . This book was released on 1969 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: Brownian diffusion of particles with Knudsen number large compared to one is analyzed both in equilibrium and nonequilibrium environments. For air in equilibrium it is shown, using only Newton's laws and the central limit theorem that for specular reflection of the molecules, equipartition is a consequence of the motion. For diffuse reflections the diffusion coefficient is found to depend upon the temperature of the particle and on the number of molecules reflected diffusely. This illustrates a limitation of the fluctuation-dissipation theorem. The motion of Brownian particles in air that is in thermal and translational nonequilibrium, is influenced by heat flux and viscous stress. A new force is described which is similar to that used to explain the thermophoresis effect but which depends upon the viscous stress. The solution is found to the new Fokker-Planck equation. In the generalized convective-diffusion equation, the diffusion coefficient appears as a second order tensor and contains the influence of the viscous stress tensor on diffusion.