Sedimentation behavior of a spherical particle in a Giesekus fluid: A CFD–DEM solution

Abstract

Abstract The sedimentation of a spherical solid particle in viscoelastic fluids was studied using a Giesekus model by development of a direct numerical simulation solver based on fully-resolved and immersed boundary methods to understand the complex non-Newtonian fluid flow and spherical particle dynamics. Two benchmark problems were modeled to evaluate the accuracy of the developed solver and excellent agreement with prior experimental and simulation results were obtained. In addition, the temporal and spatial order of convergence of the transient and advection discretization schemes were studied. The aim is to provide a clearer picture for the effect of confinement and rheology of the viscoelastic fluid on the sedimentation phenomenon of a spherical particle in a Giesekus fluid. We report that the negative wake occurs at Weissenberg number Wi ≥ 2.45 at all blockage ratios a ∕ R = 0 . 243 , 0.390, 0.464, and 0.538. At Wi = 1 . 00 , the negative wake occurs mainly at blockage ratio a ∕ R ≥ 0.390 when the effect of confinement is enhanced. There is a linear relationship between the sphere overshoot/steady-state velocity and blockage ratio due to shear-thinning effects. The oscillations in the sphere velocity were reported at all Wi for blockage ratios a ∕ R ≤ 0.464. The sphere velocity oscillations disappear at the highest blockage ratio a ∕ R = 0 . 538 except at Wi = 0 . 01 and 1.00. The viscoelastic fluid velocity oscillations were reported at Wi ≥ 1.00 at all blockage ratios. The viscoelastic fluid velocity oscillations become more damped with blockage ratio a ∕ R which the mutual effects of shear-thinning and wall effects become more dominant.