Investigation of the Weissenberg effect in ferrofluids under microgravity conditions

Abstract

We have investigated the appearance of normal stress forces in kerosene-based ferrofluids by observation of the rise of a free fluid surface at a rotating rod. The balance between centrifugal and normal stress forces inside the sheared ferrofluid — causing the so-called Weissenberg effect — is controlled by an applied magnetic field by means of changes in the fluid microstructures. The observed rise of the ferrofluid surface depends on field strength, shear rate, and amount of chain building bigger particles. The experiment had to be carried out under conditions of reduced gravity during parabolic flights.