On the two-dimensional splashing experiment for Newtonian and slightly elastic liquids

Abstract

When a solid sphere is dropped from some distance above the free surface of a liquid, a rich sequence of events can occur, the most notable being a vertical jet, which can rise some distance above the free surface. The height of this so-called Worthington jet can be dramatically reduced if a very small concentration of a high molecular weight polymer is added to a Newtonian solvent. This reduction has been tentatively linked to the high extensional viscosity of very dilute polymer solutions [J. Non-Newtonian Fluid Mech. 86 (1999)]. If this interpretation is correct, it is clearly of interest to study the corresponding planar situation, when the sphere is replaced by a long rod. In this case, a study of the height of the jet should provide information concerning the planar extensional viscosity. The experiments conducted in the present study seem to indicate that planar jets are not significantly affected by the addition of polymer additives, in contrast to the axisymmetric situation. This would indicate that the dependence of the planar extensional viscosity on polymer additives is not nearly as strong as is the case of the uniaxial extensional viscosity, although more theoretical work is required to confirm this conjecture. In the course of the experiments carried out in the present study, jets of unusual and provocative shapes were obtained when short rods were employed.