Measurement of the shear storage modulus and viscosity of liquids using the Bleustein–Gulyaev wave

Abstract

In the article, a method for measuring the rheological properties of viscoelastic liquids using the (surface shear) Bleustein–Gulyaev (B–G) wave is presented. By applying the perturbation method, one can prove that the change in the complex propagation constant of the B–G wave produced by the layer of viscoelastic liquid loading the waveguide surface is proportional to the shear acoustic impedance of the liquid. From the analysis performed by the authors, it results that the sensitivity of the B–G wave method used to determine the rheological parameters of the liquid is even higher than the sensitivity of the Love wave method. In this article, a practical measuring setup employing the B–G wave for the purpose of measuring the rheological properties of the liquid is presented. Subsequently, by measuring the change in the velocity and attenuation of the B–G wave, the shear impedance of the liquid was evaluated. Knowledge of the shear impedance of the investigated liquid then made it possible to calculate, for a given rheological model, the shear storage modulus μ and viscosity η of the investigated liquid. Measurements of liquid viscosity performed using the B–G wave method were compared to those obtained from the static capillary (Ubbelohde) method.