Flow Characteristics of Sediment Suspension in a Two-Dimensional Channel with the Presence of an Elbow

摘要

This work aims to study a flow of viscoplastic fluid in a two-dimensional (2D) 90 degree elbow at Re = 100 and Re = 1000 using a numerical approach. The fluid investigated is of sediment/clay suspension exhibiting yield stress characteristics. Bentonite-water suspension 7.5-15wt% and laponite-water suspension 3.5-5wt%, which correspond Bn = 19.76-1470.94 at Re = 100 and Bn = 1.976-147.09 at Re = 1000, are used for simulations. To model the viscoplastic effect, Herschel-Bulkley’s bi-viscosity model for Bingham type is employed. Various flow aspects, i.e., viscosity distribution, streamline pattern, formation of unyielded zones, and pressure distribution, are presented and analyzed in detail. Results show that at Re = 100, neither circulation wake nor static rigid zone is formed in the flow field pattern meanwhile at Re = 1000, the static rigid zone exists at Bn = 6.83 (bentonite 7.5wt%) and Bn = 20.88 (bentonite 10wt%). Moreover, the moving rigid zones generally become larger with the increasing Bn. Furthermore, results for pressure loss per length and friction factor are reported. Approximation functions for pressure loss estimation are also proposed.