Weissenberg Effect in Ferrofluids

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In the Weissenberg effect, a non-Newtonian fluid tends to climb up the walls of a spinning rod. This effect is usually illustrated by a ferrofluid (magnetic fluid), as in this Demonstration. Rotating a rod in a ferrofluid above some critical angular velocity exhibits this phenomenon.


The user can select the cylinder (rod) radius, the critical radius, the angular velocity of the rod, and the gravitational acceleration . The height of the liquid on the rod is determined by these variables.

For Newtonian fluids, inertia would dominate and the fluid would move away from the rod. For polymers in solution and for ferrofluids, however, the elastic forces generated by the rotation of the rod cause stretching of the polymer chains, resulting in an inward force. Thus the fluid rises up around the rod.


Contributed by: Vighnesh Souda (January 2015)
Open content licensed under CC BY-NC-SA



The equation for the Weissenberg effect is


where is the height that the liquid will reach on the rod, is the radius of the rod, ω is the angular velocity of the rod, is the gravitational acceleration, and is the critical radius.


[1] W. S. Harvie. "AP Physics C Notes." (Jan 20, 2015) teachers.sduhsd.net/tpscience/physics/notes/AP Physics C Notes - Mechanics/118 - 161 Rotations.pdf.

[2] S. Odenbach, T. Rylewicz, and H. Rath, "Investigation of the Weissenberg Effect in Suspensions of Magnetic Nanoparticles," Physics of Fluids,
 11(10), 1999 p. 2901. doi:10.1063/1.870148.

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