Numerical study of turbulence on drag coefficient determination for particle agglomerates

Abstract

Numerical simulations of the flow surrounding particle agglomerates were carried out using computational fluid dynamics to assess the ability of five RANS turbulence models to estimate the drag coefficient in particle agglomerates. Simulations were carried out in steady conditions for Reynolds numbers between 1 and 1500. Streamlines showed that symmetrical agglomerates present a velocity profile similar to the single sphere profile. Results showed that both Spalart-Allmaras and SST k-? turbulence models can represent the flow profile not only in the regions near and far from the walls of the agglomerates but also the wake region in the rear of the agglomerates. The RNG k-? model showed poor quality to predict both the velocity profile and the drag coefficient. The drag coefficient obtained by simulations presented a trend better represented by the Tran-Cong model, also showing that deviations from the predictions decreased as the packing density of the agglomerate increased. The use of steady RANS simulations showed to be a feasible and efficient method to predict, with low computational cost, the drag coefficient in particle agglomerates. For the transition and turbulent flows, results presented good agreement, with deviations between -15% and 13%, while for lower Reynolds numbers, deviations varied between -25% and 5%.