In this work, aqueous suspensions of 1% and 1.5% by weight Laponite and a blend of 0.5%/ 0.07% Laponite/ CMC are investigated in terms of their rheology and their hydrodynamic behaviour in a pipe flow.

The viscometric viscosity was measured for all fluids, but due to the fluid thixotropy a flow-equilibrium procedure was adopted. All fluids were viscoplastic and the measurement of the yield stress was carried out by direct and indirect methods. The yield stress values were of 0.93, 2.13 and 3.4 Pa for the 1% Laponite, 0.5/0.07% Laponite/CMC blend and 1.5% Laponite suspensions, respectively. The oscillatory tests shows that the 1% Laponite suspension is inelastic but the other two suspensions exhibit some elasticity.

All solutions exhibited drag reduction with the difference between the total and shear-thinning drag reductions (DR – DRv) of the order of 10% to 20% for both pure laponite suspensions but increasing to 25 to 30% for the laponite-polymer blend. For the pure clay suspensions, and based also on evidence from the literature, it was speculated that DR – DRv, could be due to a strong decrease of the viscosity associated with a turbulence-induced destruction of the internal structure plus a second mechanism more akin to that found with drag reducing polymer solutions.

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