Weissenberg effect

In fluid dynamics, the Weissenberg effect is a phenomenon that occurs when a spinning rod is inserted into a solution of elastic liquid. Instead of being thrown outward, the solution is drawn towards the rod and rises up around it.^[1] This is a direct consequence of the normal stress that acts like a hoop stress around the rod. The effect is a common example of non-Newtonian fluid dynamics, which has been shown to occur for polystyrene.^[2]

However, it is not always necessary to insert a rod to observe this effect. A rotating disk at the bottom of a viscoelasticnon-Newtonian fluid can produce a similar phenomenon: the fluid rises at the center, whereas a Newtonian fluid forms a depression,^[3] as seen when stirred with a magnetic stirrer.

The height of the fluid at the center increases with both the rotational speed of the disk and the elasticity of the fluid.^[4]

The effect is named after Karl Weissenberg who published about it in 1947.^[5]

• The Isolation of, and the Initial Measurements of the Weissenberg Effect