Fluidisation characteristics of lactose powders in simple turbulent channel flows

A new experimental platform is presented which enables investigation of the effects of turbulence, mean forces and powder properties on the fluidisation of lactose powders as relevant to pharmaceutical applications. The flow consists of a fully developed channel flow which delivers a well-defined velocity profile over a bed of powder. An in-house two beam line of sight attenuation method has been developed to extract quantitative information on powder fluidisation time, time-resolved fluctuations in powder concentration and frequencies associated with the powder fluidisation process. Four lactose powders are examined which have a range of mass mean diameters and cohesiveness. Reynolds numbers from approximately 9000 to 20,000 are examined in this study, representing one of a few quantitative examinations of lactose powder behaviour in a simple canonical flow, where the boundary conditions are well-defined and the flow is intentionally simple. Evacuation times show dependence on the Reynolds number varied both through changing the local velocity and channel dimension, whereas the Reynolds number dependence weakens at higher Reynolds numbers. Frequencies measured show physical consistency with theoretical frequencies defined through the turbulent velocity and characteristic length-scale of the powder pocket.