CFD simulation of dilute gas-solid two-phase flows with different solid size distributions in a curved $90^\circ $ duct bend

Abstract

Computational fluid dynamics predictions of dilute gas-solid flow through a curved 90 ? duct bend are performed. Flows with two different size distributions of glass spheres having mean diameters 66 ?m and 77 ?m are considered. The curved bend is square-sectioned (150 mm?150 mm) and has a turning radius of 1.5 times the duct's hydraulic diameter. Turbulent flow quantities at Re = 15,000 are calculated based on a Differential Reynolds Stress Model, while a Lagrangian particle tracking model predicts solids velocities. The model makes use of a modified shear-slip lift force formula which is consistent with experimental observation for 0.18 ? Re p ? 8. The predictions are compared against experimental measurements taken using laser-Doppler Anemometry. The study indicates that the predicted gas-solid flow behaviour near the outer wall is strongly dependent upon particle size fractions. Prediction quality deteriorates near the inner wall of the bend where local solids concentration diminishes and this points to a major limitation in the Lagrangian particle tracking methodology. The measured particle velocities at the inner wall region is found to be insensitive to the particle size distribution.