CFD-DEM modeling of dry powder inhalers using micro-models
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Applied mechanics (MPAME), MSc
Publicerad
2018
Författare
Wasberg, Emelie
Gaggini, Elly Lucia
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The continuous increase in computational power and the development of new particle models within Computational Fluid Dynamics (CFD) have made it feasible to use CFD as a complement to the physical testing in inhaler design. However, there are still challenges when simulating dry powder inhalers with carrier-based drug formulations due to the large number of fine active drug particles. An alternative approach is to model fine particles using so-called micro-models. These micro-models were coupled to a commercial CFD-DEM software that simulates the air ow and the carrier-particles. The micro-models describe the behaviour of fine particles in three different situations based on the dynamics of the carrier particle they are attached to. The first situation is the collision of a covered carrier particle against a wall causing the detachment of fine particles to the air and the attachment of fine particles to the wall. The second and third situations that cause detachment of fine particles are the collisions against other carrier particles and the drag force acting on the carrier particle exerted by the uid ow. The fine particles detached into the air, follow the air ow and are tracked with a scalar transport equation. The mentioned modeling approaches were used to study two generic geometries loaded with a drug dose and with pressure drop and ow rate relevant for real inhalers. Experiments were performed on the two geometries and the CFD-DEM simulations were set up to mimic the experimental conditions by using the same ow rate and the same material properties of the drug formulation. Additional simulations were performed as sensitivity analyses. In the first sensitivity analysis, the effect of modeling the carrier particles using parcels compared to simulating them individually was studied. In the second sensitivity analysis the effect of the material properties of the drug dose was investigated by increasing the surface energy five times in the interaction between fine particles, carrier particles and walls. In the third sensitivity analysis the importance of the diffusive transport of fine particles was evaluated by increasing the diffusion coefficient. The results of the simulations showed that the implementation of micro-models was successful as the fine particles behaved as expected based on the dynamics of the carrier particles. The most important mechanism for the detachment of fine particles was the collisions of carrier particles against walls for both studied geometries. Further, the change in material properties, together with the design of the geometries, had a large effect on the results of the simulations, indicating that they must be taken into account concurrently to predict the performance of an inhaler device. The two geometries yielded a slight difference in results in terms of free fine particles emitted from the device in the numerical simulations. However, this difference was to small to be captured in the experiments, who also showed large variability in results between different tests.
Beskrivning
Ämne/nyckelord
Strömningsmekanik och akustik , Grundläggande vetenskaper , Hållbar utveckling , Fluid Mechanics and Acoustics , Basic Sciences , Sustainable Development