Investigation of the influence of frictional viscosity regularization on quasi-static gas-solid flow predictions in a conical spouted bed with non-porous draft tube

• Published in: Advanced powder technology : the international journal of the Society of Powder Technology, Japan Japan, 2018-12, Vol.29 (12), p.3291-3304
• Main Authors: Konan, N’dri A., Huckaby, E. David
• Format: Article
• Language: English
• Subjects: [formula omitted]-rheology; Frictional flow; Inertial number; MATERIALS SCIENCE; Spouted bed; Viscosity regularization
• ISSN: 0921-8831; 1568-5527
• DOI: 10.1016/j.apt.2018.09.005

[Display omitted] •Viscosity regularization of zero strain singularity of quasistatic stress models.•Monotonic convergence of the predictions as the regularization parameter is reduced.•Higher errors with the smoother regularization function than the cutoff function.•Prediction errors dependent on predicted extent and staticity of quasistatic region. The stress in the quasi-static particle flow is often modeled through the Mohr-Coulomb failure criterion. In the extension to complex three-dimensional flows, a granular viscosity is introduced through a tensorial rheology and the deviatoric frictional stress tensor is assumed aligned with the strain rate tensor. This granular viscosity is singular as the shear rate approaches zero, regardless of the local rheology. We discuss the influence of regularizing such a frictional viscosity on the particle circulation rate and other measured characteristics in a laboratory scale draft tube spouted bed. The friction between particles is modeled either with a constant Coulomb rheology or using a local particle pressure and strain-rate based friction known as μI-rheology. The predictions appear very dependent on the regularization parameter introduced by the method. The mean properties of the flow (e.g. circulation and pressure drop) monotonically converge towards the measurements when the regularization parameter tends to zero. In other respects, the two regularization models regarded in this study induced similar hydrodynamics within the spouted bed of interest. But the analysis of the conditional averages of the inertial number and the fraction of the solids in the quasi-static regime shows that the extent and staticity of the quasi-static region is sensitive to changes to the regularization parameter or regularization function.