New ultrasonic Bleustein-Gulyaev wave method for measuring the viscosity of liquids at high pressure

Abstract

In this paper, a new method for measuring the viscosity of liquids at high pressure is presented. To this end the authors have applied an ultrasonic method using the Bleustein-Gulyaev (BG) surface acoustic wave. By applying the perturbation method, we can prove that the change in the complex propagation constant of the BG wave produced by the layer of liquid loading the waveguide surface is proportional to the shear mechanical impedance of the liquid. In the article, a measuring setup employing the BG wave for the purpose of measuring the viscosity of liquids at high pressure (up to 1 GPa) is presented. The results of high-pressure viscosity measurements of triolein and castor oil are also presented. In this paper the model of a Newtonian liquid was applied. Using this new method it is also possible to measure the viscosity of liquids during the phase transition and during the decompression process (hysteresis of the dependence of viscosity on pressure).

The equation of state of triolein up to 1 GPa

“…The phase transition was also manifested by the drop in dielectric permittivity. The measurement of viscosity [9,10] also confirms the hypothesis of solidification of triolein (after the phase transition viscosity is about 50 times larger than before). In the present study, the authors decided to extend the range of temperatures of P -V measurement.…”

“…The experiments were carried out in a 17 mm chamber, similar to the one applied for experiments described in [1,9,10] and mechanically compatible with it. The main difference was the improvement of the thermal isolation and enlargement of thermostating bath space around the chamber.…”

“…It is very likely that in natural vegetable oils under high pressure, a similar process of molecule ordering takes place. In this situation, the triolein was extensively investigated in our laboratory [6][7][8][9][10]. Also the P -V characteristics were measured at temperature 20 • C [1,8].…”

Investigation of high-pressure phase transitions in vegetable oils by measuring phase velocity of longitudinal ultrasonic waves

“…by the measurement of the viscosity [2][3][4] or the acoustic wave phase velocity in function of hydrostatic pressure.…”

Employment of a novel ultrasonic method to investigate high pressure phase transitions in oleic acid

“…After successful application of ultrasonic methods for the viscosity measurement at high pressure conditions using surface waves (Bleustein-Gulyaev and Love waves) [6,7], we have developed a method of sound velocity measurement based on our experience from such experiments. The first measurements of sound velocity under pressure using this method were done in triolein within a pressure range up to 650 MPa [8].…”