Rod-Climbing Effect in Newtonian Fluids

Abstract

When a rotating rod is brought into a polymer melt or concentrated polymer solution, the meniscus climbs the rod. This spectacular rod climbing is due to the normal stresses present in the polymer fluid and is thus a purely non-Newtonian effect. A similar rod climbing of an interface between two fluids has therefore been taken as a signature that one of the fluids exhibits normal stress effects. We show here, however, that the effect can occur with simple Newtonian fluids: it occurs when a Taylor-Couette instability happens in the less viscous of the two liquids but not in the more viscous one.

Stability of Two Axially Superposed Fluids of Different Viscosities between Two Rotating Cylinders

“…However, the difference is not more than 2%. Therefore, for this configuration the assumption made by Bonn et al (2004) Next, examining how the eigenmode varies with change in the viscosity ratio. The radial component of velocity at r = (R 1 + R 2 )/2 as a function of z is shown in Fig.5.…”

“…Therefore, present analysis does not explain the phenomenon of rod climbing completely. In the experimental setup of Bonn et al (2004) the total height of the two liquid columns was 90 mm while the gap between the cylinders was 25 mm. Accordingly L/d = 45/25 = 1.8 has been taken for numerical calculation.…”

“…Present aim is to determine at what value of Ω instability sets in for infinitesimal disturbances. In the original experiment of Taylor (Taylor 1923) for one fluid as well as in the recent experiments of Bonn et al (2004) for two superposed fluids, instability is observed to first set in as an axisymmetric mode. Accordingly, present analysis is restricted to axisymmetric disturbances.…”

“…The dynamics of two immiscible fluids between two rotating coaxial cylinders has been studied by Bonn et al (2004). Where, in the unperturbed state, the interface between the two liquids was planar and perpendicular to the axis of the cylinders.…”

Visualization of transient interfacial waves induced by spin-up of two immiscible fluid layers

“…When a cylindrical container filled with two liquids starts to rotate from rest, each phase displaces and begins to experience convection depending on the combination of two properties, and waves propagate on the phase interface. When there are two different immiscible fluids in the process, sharp changes in these properties on the interface provide various unpredictable nonlinear phenomena (Bonn et al 2004). The interfacial motion is induced by centrifugal acceleration, and the motion alters the ambient fluid flow at the same time.…”