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Issue 15, 2012
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Yielding dynamics of a Herschel–Bulkley fluid: a critical-like fluidization behaviour

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Abstract

The shear-induced fluidization of a carbopol microgel is investigated during long start-up experiments using combined rheology and velocimetry in Couette cells of varying gap widths and boundary conditions. As already described in [Divoux et al., Phys. Rev. Lett., 2010, 104, 208301], we show that the fluidization process of this simple yield stress fluid involves a transient shear-banding regime whose duration τf decreases as a power law of the applied shear rate [small gamma, Greek, dot above]. Here we go one step further by an exhaustive investigation of the influence of the shearing geometry through the gap width e and the boundary conditions. While slip conditions at the walls seem to have a negligible influence on the fluidization time τf, different fluidization processes are observed depending on [small gamma, Greek, dot above] and e: the shear band remains almost stationary for several hours at low shear rates or small gap widths before strong fluctuations lead to a homogeneous flow, whereas at larger values of [small gamma, Greek, dot above] or e, the transient shear band is seen to invade the whole gap in a much smoother way. Still, the power-law behaviour appears to be very robust and hints to critical-like dynamics. To further discuss these results, we propose (i) a qualitative scenario to explain the induction-like period that precedes full fluidization and (ii) an analogy with critical phenomena that naturally leads to the observed power laws if one assumes that the yield point is the critical point of an underlying out-of-equilibrium phase transition.

Graphical abstract: Yielding dynamics of a Herschel–Bulkley fluid: a critical-like fluidization behaviour

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Publication details

The article was received on 07 Oct 2011, accepted on 22 Jan 2012 and first published on 01 Feb 2012


Article type: Paper
DOI: 10.1039/C2SM06918K
Citation: Soft Matter, 2012,8, 4151-4164
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    Yielding dynamics of a Herschel–Bulkley fluid: a critical-like fluidization behaviour

    T. Divoux, D. Tamarii, C. Barentin, S. Teitel and S. Manneville, Soft Matter, 2012, 8, 4151
    DOI: 10.1039/C2SM06918K

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