Motion of liquid drops in rheologically complex fluids

Abstract

The influence of viscoelasticity and of the shear-dependent viscosity of ambient liquids on the motion of liquid drops was examined experimentally. In the low Reynolds number region (Re < 1) the influence of elasticity is insignificant and the influence of the variable viscosity is well accounted for by the existing correlations. At higher Reynolds number (Re > 1) the viscoelasticity brings about a substantial increase of drag. An interpretation of this phenomenon is attempted in view of the changes of the wake behind the drop and an empirical correlation in terms of the Weissenberg number is suggested. Additionally it was found that the "wave theory" as presented by Marrucci et al⁽⁸⁾ can be satisfactorily used for drops moving at Re > 10 irrespective of rheological complexities.