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Abstract
This work presents a numerical study on two types of commercial inhalers, Aerolizer® and
Turbuhaler® inhalers. A coupled Computational Fluid Dynamics (CFD) and Discrete
Element Method (DEM) technique was adopted to simulate fluid flow and particles,
respectively, for the Aerolizer® inhaler. The results showed that the shear stress of
turbulent flow had no visible effect on powder dispersion while the agglomerateagglomerate
interactions occurred only when the agglomerates were ejected from the
capsule. Between the agglomerates and the wall, many major impactions occurred
resulting in fragmentation of agglomerates into large pieces without generating many fine
particles. The subsequent impaction with the inhaler grid also contributed to an increase in
FPF (amount of fine particles below 5 μm in the aerosol). It was observed that the inhaler
was more efficient in terms of FPF with increasing airflow rate but FPF decreased at a
higher flow of 130 L/min due to larger deposition inside the inhaler.
The study on the Turbuhaler® inhaler was approached using CFD coupled with Discrete
Phase Modelling (DPM). The effects of key variables associated with airflow rates and
particle sizes were investigated. It was found that smaller particles moved faster in the
inhaler and experienced more impactions. However their impact energy was low. Larger
particles, while having large impact energy, were more inclined to be traveling slower
inside the inhaler. FPF generated from the inhaler increased with increasing airflow rates
but powder deposition also increased with larger air flowrate.
This study has highlighted an important role of numerical modelling techniques such as
CFD-DEM to provide further insight into the effect of airflow inside DPIs and the
subsequent effect on particles travelling inside the inhaler. This allows a rational basis for
future improvement of inhaler devices.