Agitation of Complex Fluids in Cylindrical Vessels by Newly Designed Anchor Impellers

The fluid flows and power consumption in a vessel stirred by anchor impellers are investigated in this paper. The case of rheologically complex fluids modeled by the Bingham-Papanastasiou model is considered. New modifications in the design of the classical anchor impeller are introduced. A horizontal blade is added to the standard geometry of the anchor, and the effect of its inclination angle (α) is explored. Four geometrical configurations are realized, namely: α = 0°, 20°, 40°, and 60°. The effects of the number of added horizontal blades, Reynolds number, and Bingham number are also examined. The obtained findings reveal that the most efficient impeller design is that with (case 4) arm blades inclined by 60°.This case allowed the most expansive cavern size with enhanced shearing in the whole vessel volume. The effect of adding second horizontal arm blades (with 60°) gave better hydrodynamic performance only with a slight increase in power consumption. A significant impact of Bingham number (Bn) was observed, where Bn = 5 allowed obtaining the lowest power input and most expansive well-stirred region.

Regularization models for natural convection of a pseudoplastic liquid in a closed differentially heated cavity

Simulation of convective heat and mass transfer in systems filled with pseudoplastic fluids deals with computational difficulties due to the appearance of an infinite level of effective viscosity as the intensity of deformation rates tends to zero. To solve this problem, various regularization models are used by introducing a small additional term into the expression for the effective viscosity. The present research is devoted to analysis of widespread regularization models for studying the natural convection of a pseudoplastic fluid in a closed differentially heated cavity. The pseudoplastic nature of the fluid flow was described by the Ostwald-de Waele power law. Three regularization models were investigated, namely, the simplest algebraic model, the Bercovier and Engleman model, and the Papanastasiou model. The boundary value problem of mathematical physics formulated using the conservation laws of mass, momentum and energy, was solved by the finite difference method. The obtained results were compared with data of other authors.