The laminar/turbulent transition for paste sheet flow

Abstract

The sheet flow of paste material is of critical importance in tailings disposal, since this is the principal flow mechanism at tailings disposal sites. Furthermore, the sheet flow paradigm for free surface flows has the potential to provide a basis for analysis and design for the open channel flow of mineral tailings suspensions. In our previous studies, we showed that a sheet flow diagram could be constructed, and that it is directly related to the rheogram in a manner analogous to that of Rabinowitsch and Mooney for tube flow. Furthermore we showed that these flows could be scaled for engineering design purposes in a manner similar to the approach of Metzner and Reed for tube flow. Whilst some progress has been made for the rheometrical measurement and analyses of sheet flow, many unresolved issues remain. Arguably, the most acute of these is the location of the Laminar/Turbulent transition. The objective of this paper is to develop and evaluate an approach for the analysis of the Laminar/Turbulent transition of sheet flows. Building on our previous studies, a new Reynolds number approach for sheet flows of general non-Newtonian material is developed and presented. Using experimental data, it is shown that this approach works well for power law fluids, and extension of this approach for the analysis of viscoplastic materials is discussed. Further work involving the role of the yield stress in the transitional flow process is being undertaken.