Transient response of concentrated suspensions after shear reversal

Abstract

We have examined the transient stress response under shear flow of concentrated suspensions of non-Brownian spheres. We focused on the experiment where the shearing is momentarily stopped and restarted in the opposite direction. We found that the normalized stress recovery curves for different values of the initial and subsequent shear rates could be collapsed quite well if plotted against the strain. This behavior agrees with the basic concept that the transient stress behavior is a function only of the imposed strain, as predicted by some recent constitutive models of concentrated suspensions. We also found that the transient behavior of the normal stress difference showed similar data collapse. Further, there appeared to be little qualitative difference in the behavior of particulate systems with a high degree of size monodispersity and those more polydisperse.

A new rate-independent tensorial model for suspensions of noncolloidal rigid particles in Newtonian fluids

“…Their model nevertheless also involves 13 free parameters. These authors obtained numerical results in qualitative agreement with a shear reversal experiment [7,31], but failed to obtain quantitative comparisons. In contrast with SBM model, all these tensorial models are, by construction, frame-invariant and potentially applicable to arbitrary flow geometries and conditions.…”

“…In 2006, Goddard [28] revisited this approach, and proposed a model involving twelve material parameters and two tensors for describing the anisotropy. By a systematic fitting procedure of the parameters, he obtained numerical results in quantitative agreement with shear reversal experiments [7,31]. Also in 2006, Stickel et al [34] (see also [35,36]) defined the conformation tensor on the base of particle mean free path, and simplified the expression of the stress to be linear in the deformation rate and the conformation tensor.…”

“…[29]). For concentrated suspensions of spherical particles, Phan-Thien [30] proposed a differential constitutive equation for the conformation tensor, that led to prediction qualitatively in agreement with time-dependent experimental observations in shear reversal [6,7,31]. The structural unit used to define the conformation tensor was taken as the unit vector n joining two neighboring particles, thereby encoding a direct connection with the pair distribution function g(x).…”

“…Conversely, if the shear rate restarts suddenly in the direction opposite to its previous value, e.g. −γ 0 , experimental observations by Narumi et al [31], Fig. 3, showed that particle pressure p p progressively increases from zero to its previous stationary value while shear stress σ xy progressively decreases from zero to the opposite of its previous stationary value.…”

Microstructure in sheared non-Brownian concentrated suspensions

“…Indeed, when particles are added to a Newtonian fluid, besides the quite well documented increase of the shear viscosity, a drastic change of the rheological behavior, including normal stress differences is observed. The concept of shear-induced microstructure has been introduced for the first time by Gadala-Maria and Acrivos (1980) to explain the transient rheological response of concentrated suspensions under shear reversal (see also [Kolli et al (2002); Narumi et al (2002); Blanc et al (2011b)…”