Flow of a Thixotropic Bingham Fluid over a Cylinder in Stationary and Non-Stationary Regimes

Flow of a thixotropic Bingham liquid over a cylinder is investigated in this work. Thixotropy is a rheological characteristic associated with the microstructure of the material, which can be broken and recovered during a flowing process. Various flow characteristics such as the flow morphology, the unyielded/yielded zones, the microstructural state, and the hydrodynamic forces acting on the cylinder are analyzed at Re = 20–100 and Bn = 0.5–10. Comparison with Newtonian and non-thixotropic Bingham fluids are also carried out and discussed. Results show that, within these conditions, the flow spans from a stationary regime with or without separation to a non-stationary laminar one with von-Karman-type vortex shedding. In addition, no near-field unyielded zones are observed at Re = 100 and Bn = 0.5 and 1, probably due to the unsteady nature of the flow. At conditions where static unyielded zones exist, the wall shear stress normalized by the yield stress is minimum within these structures.