Dilute gas–solid two-phase flows in a curved 90∘90∘ duct bend: CFD simulation with experimental validation

Computational fluid dynamics (CFD) simulations of dilute gas–solid flow through a curved 90∘90∘ duct bend were performed. Non-uniform sized glass spheres with a mean diameter of 77μm were used as the dispersed phase. The curved bend is square-sectioned (150mm×150mm) and has a turning radius of 1.5D(D=duct hydraulic diameter). Turbulent flow quantities for Re=100,000Re=100,000 were calculated based on a differential Reynolds stress model. The solids mass loading considered is 0.00206 and hence justifies the application of one-way coupling between gas and particles. A Lagrangian particle-tracking algorithm which takes into account the effect of shear-slip lift (SSL) force on particles and particle-wall interactions (PWIs) has been utilised to predict velocities of the dispersed phase. The predictions were compared against the experimental data measured using Laser–Doppler Anemometry (LDA). The study found that the predicted gas flow field has a strong influence over the predicted particle velocities. PWI model considerably affects the prediction of particle velocity and distribution of particles at the inner duct wall within the bend. Inclusion of the SSL force also helps the distribution of the particle tracks towards the duct centre in the vertical duct downstream of the bend. Within the bend, particle velocities near the inner wall have been grossly over-predicted in the simulation, especially at mid-bend. The present study thus highlights the importance of the predicted gas flow field, SSL force and particle-wall collisions to Lagrangian particle tracking.