Particle migration in concentrated suspensions undergoing squeeze flow

Abstract

When a fixed volume of a pure viscous fluid is squeezed between two parallel circular plates under a constant force, in the absence of surface tension, the radius of the propagating fluid front R increases such that R8 is linear in time t in the lubrication limit [Engmann, J., C. Servais, and A. S. Burbridge, “Squeeze flow theory and applications to rheometry: A review,” J. Non-Newtonian Fluid Mech. 132, 1–27 (2005)]. However, when the experiment is repeated with a suspension of rigid spheres instead of the pure viscous fluid, the behavior deviates from this R8 vs t relationship at a radius Rm. This deviation is followed by the appearance of an instability in the azimuthal direction at the propagating suspension interface at a radius Ri. The instability arises due to the establishment of radial concentration and therefore viscosity gradients during the squeeze flow, which are susceptible to miscible viscous fingering [Tang, H., W. Grivas, D. Hometocovschi, J. Geer, and T. Singler, “Stability consideration...