1. Results A visual analysis reveals two distinct modes of evacuation for different particle types regardless of geometry or pressure ramp gradient. Cohesion-less glass spheres (depicted at the top of this poster) and aluminium flakes evacuate through an erosion mechanism, a regular stream of individual particles. A highly cohesive lactose 15.8% fines blend (depicted at the foot of this poster) evacuates through a fracture mechanism, agglomerated lumps of particles fracture from the main bed in an irregular fashion. A lactose 6.0% fines blend exhibit a mixed behaviour between the two modes. Some quantitative analysis has been possible by plotting the normalised image intensity of the pocket area against pressure over the course of an evacuation. Application of this method to the lactose 15.8% fines blend (90 degree geometry) for three different pressure ramps generates the plot featured above. This plot suggests the extent of evacuation is dependent on the current pressure only, and is independent of the pressure gradient. Unfortunately this method cannot be applied to erosion mode evacuations due to hidden 3D effects. Dry Powder Inhaler Flow Visualization Rob Tuley, John Shrimpton, Mark Palmer Objectives The ultimate aim of our research is to computationally simulate the evacuation of particles from dry powder inhalers, with a particular focus on the current GSK Diskus design. This poster highlights recent experimental work undertaken in an attempt to establish how pockets of stationary particles behave under the influence of a patient inhalation, and what parameters affect this behaviour. Conclusions Both glass and aluminium particles exhibit almost identical behaviour suggesting that inter-particle cohesion forces have a more significant affect on the evacuation than particle shape. Initial quantitative results suggest evacuations of the highly cohesive lactose 15.8% fines blend are independent of pressure ramp gradient, although this conclusion cannot as yet be extended to the other particle types tested. Experiment Setup & Design For the purpose of experimentation, simplifications are applied to the process of human inhalation and the complex internal geometry of a Diskus inhaler. An inhalation is simulated as a linear pressure ramp of specified gradient. Three simplified geometries and a replica Diskus model are tested with a range of different particle types and pressure ramp gradients. Diskus replica, 90, 45 and 0 degree simplified geometries To ensure that the desired negative linear pressure ramp is maintained throughout the transient evacuation process, the pressure at pocket outlet is controlled using a proportional and integral control feedback loop. To visualize the evacuation a Kodak high speed digital video camera is used, recording at a rate of 4500 frames per second. The pocket area in each geometry is back-lit with a halogen lamp, thus making the powder in the displayed frames at the top and bottom of this poster appear black.