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 viscoelastic non-Newtonian fluid can produce a similar phenomenon: the fluid rises at the center, whereas a Newtonian fluid forms a parabolic 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]
