Journal of the Brazilian Society of Mechanical Sciences and Engineering
Print version ISSN 1678-5878
HALDENWANG, Rainer; KOTZE, Reinhardt and CHHABRA, Raj. Determining the viscous behavior of non-Newtonian fluids in a flume using a laminar sheet flow model and Ultrasonic Velocity Profiling (UVP) system. J. Braz. Soc. Mech. Sci. & Eng. [online]. 2012, vol.34, n.3, pp. 276-284. ISSN 1678-5878. http://dx.doi.org/10.1590/S1678-58782012000300008.
The flow of non-Newtonian fluids in rectangular open channels has received renewed interest over the past number of years especially as large flumes are being used to transport tailings in countries like Chile. The effect of yield stress on the flow behavior is complex and not yet fully understood. The Ultrasonic Velocity Profiling (UVP) technique has been used to construct velocity profiles of non-Newtonian fluids flowing in a 10 m by 300 mm wide tilting flume. The contour maps were integrated to show that the velocity profiles were indeed correct. The thin film flow models available in the literature have been tested in terms of flow depth and Reynolds number. The measured profiles also show the influence of the side walls on the general flow features as the distance from the centre increases. The results reported herein span the laminar, transition and turbulent flow regions. As far as can be ascertained, it is the first time that this technique has been used to measure velocity profiles in opaque non-Newtonian fluids for open channel flow. It is shown here that, under appropriate conditions, the velocity profile and flow depth can be used to obtain the viscous properties of the fluids tested. Excellent correspondence between the rheological parameters inferred from the velocity profile measurements and that from the tube viscometry was obtained.
Keywords : open channel; ultrasound velocity profiling; sheet flow; non-Newtonian fluid; rheology.