Non-Newtonian fluids are full of all kinds of unusual behaviors. Here a highly viscoelastic non-Newtonian fluid exhibits the Barus effect, in which extruding the fluid causes the falling jet to swell to several times larger than the diameter of the opening through which it was extruded. This is caused by the stretching and relaxation of polymers in the fluid as it passes through the opening.
The Barus Effect
