Particle Motion in Non-Newtonian Fluids

Professor R. H. Rangel
Professor D. D. Joseph
Arezoo Ardekani, PhD Student

We investigate the motion of a sphere normal to a wall. The normal stress at the
surface of the sphere is calculated and the viscoelastic effects on the normal stress for
different separation distances are analysed. For small separation distances, when the
particle is moving away from the wall, a tensile normal stress exists at the trailing
edge if the fluid is Newtonian, while for a second-order fluid a larger tensile stress is
observed. When the particle is moving towards the wall, the stress is compressive at
the leading edge for a Newtonian fluid whereas a large tensile stress is observed for
a second-order fluid. The contribution of the second-order fluid to the overall force
applied to the particle is towards the wall in both situations. Results are obtained
using Stokes equations when α1 + α2 = 0. In addition, a perturbation method has
been utilized for a sphere very close to a wall and the effect of non-zero α1 + α2 is
discussed. Finally, viscoelastic potential flow is used and the results are compared
with the other methods.

Publications

Ardekani, A. M., Rangel, R., Joseph, D. D. (2007). Particle-particle and particle-wall interactions in a second-order fluid. APS Fluid Dynamics Conference.

Ardekani, A. M., Rangel, R., Joseph, D. D. (2009). Two spheres in a stream of a second-order fluid. Physics of Fluids, 20(6).