Capillary and rotational flow of a suspension of magnetic particles in the presence of discontinuous shear thickening

Georges Bossis (1) , Yann Grasselli (2) , Olga Volkova (1)

1 INPHYNI - Institut de Physique de Nice
2 SKEMA Business School

The rheology of suspensions showing discontinuous shear thickening (DST) is well documented in conventional rheometer with rotating tools, but their study in capillary flow is still lacking. We present results obtained in a homemade capillary rheometer working in an imposed pressure regime for a suspension made of submicronic iron particles (Bossis et al., 2021). We show that the shape of the experimental curve giving the volume flow rate versus the wall stress in a capillary can be qualitatively reproduced from the curve stress-shear rate obtained in rotational geometry at imposed stress but instead of a sharp decrease of the volume flow rate observed at a critical stress, this transposition predicts a progressive decrease in flow rate. The Wyart-Cates theory is used to reproduce the stress-shear rate curve obtained in rotational geometry and then applied to predict the volume flow rate at imposed pressure. The theoretical curve predicts a total stop of the flow at high stress, whereas experimentally it remains constant. We propose a modification of the theory which, by taking into account the relaxation of the frictional contacts in the absence of shear rate, well predicts the high stress behavior. We also hypothesized that the DST transition propagates immediately inside the capillary, once the wall shear stress has reached its critical value:τ(R)=τc, even if the internal shear stress τ(r

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Georges Bossis, Yann Grasselli, Olga Volkova. Capillary and rotational flow of a suspension of magnetic particles in the presence of discontinuous shear thickening. AERC 2022 The Annual European Rheology Conference, Apr 2022, Séville, France. ⟨hal-03864569⟩