An experimental study of non-Newtonian fluid flow in rectangular flumes in laminar, transition and turbulent flow regimes

New and extensive results are reported on the flow of a range of non-Newtonian fluids, including aqueous suspensions of bentonite and kaolin, and aqueous solutions of synthetic polymer carboxymethyl cellulose (CMC), flowing down inclined flumes of rectangular cross-section of three different sizes. In particular, these tests elucidate the role of shear-thinning viscosity, with and without the presence of a yield stress, on the flow behaviour in flumes over a wide range of conditions of Reynolds numbers spanning the range 1<Re<10(4), thereby embracing both the laminar and transitional flow regimes, and possibly the turbulent regimes. Furthermore, the flumes could be tilted up to 5 from the horizontal. This extensive experimental study has facilitated the delineation of the role of the Froude number in the nature of flow, as well as the cessation of laminar flow conditions in such industrially important systems. The results reported here can be used to design flumes for shear-thinning and/or viscoplastic fluids.