On the Dynamic Viscosity Coefficients and Relaxation Processes in Magnetic Fluids

Abstract

The frequency dispersion has been studied for the dynamic viscosity coefficients determined on the basis of both the Smoluchowski equation, which describes the diffusion relaxation mechanism, and the Bhatnagar–Gross–Krook approximation, which leads to an exponential damping of the stress tensor in magnetic fluids. In the former case, the Green function, which enters into the integral parts of the transport coefficients, is a slowly damped function varying in accordance with the ${{t}^{{{{ - 3} \mathord{\left/ {\vphantom {{ - 3} 2}} \right. \kern-0em} 2}}}}$ law, which has been observed in many computer-assisted experiments. Here, the range of the frequency dispersion of viscosity coefficients is very wide as a consequence of the damping of relaxation fluxes according to the power law. In the latter case, the range of the frequency dispersion of the viscosity coefficients is narrow as a consequence of the exponential damping of the stress tensor and coincides with experimental data.