Numerical study on the hydrodynamics of agglomerates at intermediate Reynolds numbers

Abstract

Abstract The flow pattern and hydrodynamics of a heterogeneous permeable agglomerate in a uniform upward flow at intermediate Reynolds numbers (1–40) are analyzed from three-dimensional (3D) computational fluid dynamics simulations. Different from the homogeneous or stepwise-varying permeability models used in previous papers, a continuously radially varying permeability model is used in the present study. The effects of two dimensionless parameters, the Reynolds number and the permeability ratio, on the flow field and the hydrodynamics were investigated in detail. The results reveal that unlike the solid sphere, a small recirculating wake initially forms inside the agglomerate. The critical Reynolds number for the formation of the recirculating wake is lower than that of the solid sphere and it decreases with the increase of permeability ratio. A correlation of drag coefficient as a function of the Reynolds number and permeability ratio is proposed. Comparisons of drag coefficients obtained by different permeability models show that at intermediate Reynolds numbers (1–40), the effect of radially varying permeability on the drag coefficient must be considered.