The present study focuses on the friction factors of a colloidal suspension flow in circular and square tubes. The colloidal suspension was made of silicon dioxide nanoparticles dispersed in distilled water at a concentration of 9.58% by volume. The viscosity and shear stress of the suspension were measured and it was found that the fluid exhibited non-Newtonian behavior. The rheological behavior of the suspension could be adequately modeled as a power-law generalized Newtonian fluid (GNF). When the consistency and the flow behavior indices of the suspension were properly evaluated, the friction factors of the suspension flowing in tubes with circular and square cross-sections exhibited similarities with those of Newtonian fluid flow. In fully-developed laminar flow, the Poiseuille number for the suspension was similar to that for a Newtonian fluid flow. In turbulent flow, the Dodge and Metzner’s relations for the friction factor and a generalized Reynolds number can be used to adequately describe the suspension in turbulent flow. Observations from the friction factor measurements showed that the onsets of transition to turbulent flow vary with the cross-sectional shape of the tube and differ from those of Newtonian fluid flow. This might suggest that the cross-sectional shape of the flow passage and the presence of nanoparticles could affect the onset of transition to turbulent flow for the suspension.

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