A Model for the Bulk Viscosity of a Liquid

A simple theory has been developed for the complex and frequency-dependent nature of the bulk viscosity of a liquid using the principle of superposition and dimensional analysis. The complex nature is a result of the phase shift between the pressure and density waves. The viscosity coefficients are obtained as functions of the frequency and velocity of the wave, the structural relaxation time of the liquid, and a new viscosity coefficient. These are compared with Stokes-Navier equations and the absorption formula. The variation of the viscosity components with frequency in both associated and nonassociated liquids is discussed. discussed. Simple formulas are obtained for the structural relaxation time as a function of the frequency and velocity of the wave and the viscosity coefficients of the medium. Calculated values of the structural relaxation time are compared with existing values, and the agreement is fairly good. © 1969 IEEE. All rights reserved.