Transfer Talk 2022

Overview

If you've made it here, then that means I can still do some HTML! Anyway, welcome to the section of my website regarding my MRes Transfer Talk on the 5th October. Here, I've added some stuff augmenting my talk.

Firstly, these are my slides from the talk. Secondly, if you want to see some cool viscoelastic phenomena, then see below!

Weissenberg Effect

Also known as the rod climbing effect, this is due to additional stresses arising in a viscoelastic fluid when it is stirred. These stresses — which are called normal stresses — act in the direction of motion, causing a tension force which pulls the fluid towards the stirring rod. An example can be found here.

Die Swell

Another effect which is observed in viscoelastic fluids is die (or extrudate) swell. This is again due to the additional normal stresses arising as the fluid flows through a pipe. These stresses generate tension, which is relieved as the resulting fluid jet leaves the pipe. As a result, the diameter of the jet can expand to a width as much as three times the pipe diameter.

Tubeless Siphon Effect

Particularly seen in polymeric fluids, this effect occurs when the fluid is stretched. In this deformation, the long-chain polymer molecules in the fluid are extended, which produces a large elastic force, which in certain cases is enough to overcome gravity and pull fluid out of a beaker!

Kaye Effect

In the Kaye effect, a jet of fluid poured onto a surface leaps on impact, rather than stagnating or coiling as one might expect. Current evidence suggests that this occurs due to the existence of an extremely thin air layer between the falling jet and the `heap' of fluid below it. This air layer acts as a lubricant, enabling the jet to slip. Viscoelasticity is said to reduce the pressure required to bend the jet (see here); therefore, enabling a larger air layer to be sustained and allowing jets to be supported for longer.

In case you're interested, this is how the talk ended.