MICROSCOPIC AND MOLECULAR SHEAR VISCOSITY

A review on the effect of Newton's macroscopic dynamic shear viscosity on the rotation of a cylinder and a ball in a viscous liquid is prese nted. The approximate nature of some of Stokes' formulas is discussed, and formulas from elementary viscosity theory are given. The concept of molecular viscosity is introduced, and it is shown that, among othe r information sources, spectra of depolarised molecular light scatteri ng and electromagnetic wave dispersion in liquids of constant-dipole-m oment molecules may, within a certain scheme, be used to derive the va lue and temperature dependence of the coefficient of shear dynamic mol ecular viscosity. As an example, the temperature behaviour of molecula r viscosity in o-terphenyl and o-fluorophenyl is presented and qualita tively discussed.