In English

CFD-DEM modeling of dry powder inhalers using micro-models

Emelie Wasberg ; Elly Lucia Gaggini
Göteborg : Chalmers tekniska högskola, 2018. Examensarbete - Institutionen för mekanik och maritima vetenskaper; 2018:35, 2018.
[Examensarbete på avancerad nivå]

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 ne active drug particles. An alternative approach is to model ne 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 ne particles in three di erent situations based on the dynamics of the carrier particle they are attached to. The rst situation is the collision of a covered carrier particle against a wall causing the detachment of ne particles to the air and the attachment of ne particles to the wall. The second and third situations that cause detachment of ne particles are the collisions against other carrier particles and the drag force acting on the carrier particle exerted by the uid ow. The ne 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 rst sensitivity analysis, the e ect of modeling the carrier particles using parcels compared to simulating them individually was studied. In the second sensitivity analysis the e ect of the material properties of the drug dose was investigated by increasing the surface energy ve times in the interaction between ne particles, carrier particles and walls. In the third sensitivity analysis the importance of the di usive transport of ne particles was evaluated by increasing the di usion coecient. The results of the simulations showed that the implementation of micro-models was successful as the ne particles behaved as expected based on the dynamics of the carrier particles. The most important mechanism for the detachment of ne 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 e ect 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 di erence in results in terms of free ne particles emitted from the device in the numerical simulations. However, this di erence was to small to be captured in the experiments, who also showed large variability in results between di erent tests.

Nyckelord: dry powder inhalers, computational uid dynamics, micro-models, discrete element method, carrierbased drug formulation, ANSYS Fluent



Publikationen registrerades 2018-08-13. Den ändrades senast 2018-09-20

CPL ID: 255692

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