Viscosity Measurement of Foam with High Gas Volume Fraction Using Sphere Pull-up and Dam-break Experiments

Abstract

Viscosity measurements of a gas-liquid two-phase fluid (foam) with fine bubbles were conducted using a sphere pull-up method and the flow behavior in dam-break experiments was evaluated. The following results were obtained.

(1) Using known silicone oil, external forces were measured to determine the conversion constants under various sphere diameters and descent speeds. Subsequently, the viscosity of the foam was measured similarly. The results indicated that the foam exhibited shear-thinning behavior and could be classified as a pseudo-plastic fluid.

(2) The viscosity of the foam showed little variation between gas volume fractions of 0.4 and 0.65 but increased significantly near 0.8. This trend was consistent with the results obtained by Hatano et al. using a rotational viscometer.

(3) In the dam break experiments, the traveling distance of the foam was proportional to time for gas volume fractions between 0.65 and 0.85, while at 0.95, the initial flow velocity was slow and increased gradually.

(4) Using the relationship between viscosity and shear rate of the foam measured by the sphere pull-up method, 3-D numerical fluid flow calculations were performed under dam-break conditions. Since the calculated time for traveling to the bottom was shorter than that of the experiment, an inverse analysis was performed to obtain a relationship between viscosity and shear rate that was compatible with the experiment. As a result, it was found that the viscosity at high shear rate was underestimated by the sphere pull-up method.