Investigation of the Weissenberg effect in suspensions of magnetic nanoparticles

We have investigated the appearance of normal stress differences in suspens ions of magnetic nanoparticles by observation of the rise of the fluid at a rotating axis. The combination nu(10)+4 nu(20) of the low shear rate limit s of the normal stress coefficients nu(10) and nu(20) has been varied by me ans of the action of a magnetic field applied to the fluid. Its value has b een determined for different shear rate and magnetic field strength. To enh ance observability of the rise of the fluids, the experiments have been car ried out under conditions of reduced gravity during parabolic flights. (C) 1999 American Institute of Physics. [S1070-6631(99)02109-1].