Diffusion effects on weak spherical disturbances in binary mixtures

Combined mass-diffusion, viscous, and thermal-conduction effects on weak spherical disturbances in inert binary mixtures are investigated by means of the linearized Navier-Stokes equations. Pressure diffusion is of special interest. Laplace-transform techniques are utilized to obtain asymptotic approximations valid for large and small times. The small-time behavior is entirely diffusive and reflects transport interactions induced by pressure diffusion. The large-time solution shows a wave behavior with diffusive wave fronts broadened by pressure diffusion. For the mass-fraction disturbance, wave behavior is a second-order contribution induced by pressure diffusion which prevails when the initial mass-fraction disturbance is zero.