Abstract Summary (Max 250 words)
In slurry transport pipelines, determining the laminar-turbulent transition velocity for an industrial slurry with a yield stress is important as it can significantly impact flow behaviour and the ability to transport solids in a pipeline. The laminar-turbulent transition velocity is directly dependent on the Bingham (or fully- sheared) yield stress of the slurry being transported. It has also been observed that the presence of coarse particles can significantly increase the yield stress of a slurry, a phenomenon dubbed yield stress augmentation. The gap in a concentric cylinder viscometer is typically much too small to accurately measure the rheology of an industrial coarse particle slurry as the particles interfere with the walls of the geometry. While we can measure the yield stress augmentation using a vane viscometer, we currently do not have an efficient and reliable method to measure the fully-sheared yield stress of a slurry that can capture the coarse particle augmentation effect. However, it has been shown from Elson et al. (1986) and other works that rotating, open impellers in yield stress fluids form caverns that will vary in diameter with the fluid yield stress, alongside other parameters. So, for a given impeller, tank geometry and impeller rotation speed, the yield stress of the fluid could be determined by measuring the cavern diameter. This work will present the development progress of an instrumented mixing setup that aims to use cavern sizes to determine the fully-sheared (Bingham) yield stress of industrial slurries with coarse particles.
