Numerical study of Bingham flow in a pipe with the presence of a baffle

Abstract

A numerical study of Bingham fluid flow in a two-dimensional (2D) pipe with a baffle is reported in this paper. Bingham fluid is a material characterized by a yield stress; it flows with a constant plastic viscosity when an applied shear stress exceeds the yield stress, and does not flow otherwise. Such a flow has many practical applications such as transport of sewage, underground drainage, oil and fresh concrete/cement in pipes or pumping systems. The studied flow is in both stationary (Reynolds − number of Re=100) and non-stationary (Re=1000) regimes with the Bingham number in the range of Bn=0-5. Various flow characteristics such as flow morphology, streamline pattern, velocity field, and vortex structure are analyzed. It is observed that at Re=100, the circulation structure behind the baffle becomes smaller as Bn increases. Unyielded (solid) zones, which are supposed to diminish the flowability and material mixing, are formed at the pipe's center and/or around the baffle; they however become larger as Bn is greater. However, at Re=1000, the solid zones are substantially reduced, hence enhancing the material mixing. In addition, effect of the baffle's length on the flow is analyzed. Major head loss due to viscous effect along the pipe and minor head loss at the baffle are also examined.