Can the Bubble Surface Tension Affect the Equivalent Viscosity of Bubbly Oil?

Abstract Equivalent viscosity is a basic parameter of the bubbly oil, however, it is a controversy whether or not the bubble surface tension should be taken into account when modeling the equivalent viscosity of bubbly oil at high shear rate. In this technical brief, the effect of bubble surface tension on the equivalent viscosity of bubbly oil is examined experimentally using the proof by contradiction. The viscosity of bubbly oil is measured using test samples with clearances in series, and the bubble distributions of the bubbly oil before and after tests are observed. The test result shows that at a high shear rate, the equivalent viscosity of bubbly oil is not sensitive to the change in the sample clearance, whereas the bubble distribution after test is dependent on the clearance, suggesting that the effect of bubble surface tension can be disregarded for the equivalent viscosity of bubbly oil at high shear rate.