Airflow simulation for inhaler design using CFD


Optimise the performance of a capsule dry powder inhaler (DPI) to increase fine particle drug delivery to the deep lung and in turn, improve the reliability of therapeutic outcomes for patients.


We used computational fluid dynamics (CFD) to simulate the complex airflow and powder dispersion within the DPI. This allowed us to inform key design changes for next-generation prototypes to be tested in the lab.


Patients can receive a more consistent dose regardless of how strongly they inhale, which helps to manage their condition more effectively.

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The challenges of dose powder delivery

Fine particle delivery is a key performance metric for the therapeutic effectiveness of a DPI. Dose powder delivered by a DPI must be dispersed into respirable particles that are small enough to successfully reach the patient’s deep lung.

The complex fluid dynamics of powder dispersion within a DPI can be challenging to simulate directly due to the vast number of turbulent airflow-to-particle and particle-to-particle interactions. However, by employing a balanced approach to simulation complexity, CFD can be a highly effective tool to inform and optimise inhaler design. We used CFD simulations to successfully improve the respirable fraction of drug delivered from a novel capsule DPI.

Capsule DPIs often represent a good option for respiratory drug delivery of powder formulations, particularly for brand-new, innovative drugs seeking an efficient route to clinical trials. However, capsule DPIs can suffer from challenges of variable fine particle aerosol performance which means that patients can receive a low dose if they don’t inhale strongly enough, potentially aggravating the disease.

A novel prototype capsule inhaler to address variable dose delivery performance

Team Consulting developed a novel prototype capsule DPI to address the challenge of variable dose delivery performance and improve the consistency of the dose reaching the deep lung despite the expected wide range of different inhalation efforts used by patients to energise the device.

CFD simulations were an indispensable tool for deep understanding of the device flow physics and to optimise the design of the capsule DPI.

Stuart Abercrombie, Senior Engineering Consultant, Team Consulting

The novel DPI harnesses a high proportion of inhalation energy for powder deagglomeration. The novel drug delivery device employs a bespoke deagglomerating swirl chamber downstream of the powder exiting the capsule. It also includes a flow straightener at the outlet of the device to reduce the swirl of particles leaving the device, which could otherwise cause detrimental side effects to the patient related to drug deposition in the mouth and throat.

Balancing Computational Fluid Dynamics simulation complexity

The CFD approach was focused on striking the necessary balance between simulation complexity and flexibility. It was essential for CFD simulations to be sufficiently accurate to provide valuable design insight, while also remaining flexible enough to support fast-paced design changes.

We started simple and increased CFD complexity only where needed in a stepwise fashion, until simulations demonstrated good agreement with lab testing of physical prototypes. Then, we could rapidly iterate and optimise the design using CFD, drawing on improved understanding and calculation of key performance metrics from the simulations. This achieved a much-improved design with faster and cheaper development timelines compared to a sole focus on building and testing prototypes.

Tight budgets and timescales often demand lean and flexible CFD simulations to support device development. It’s an important skill of the CFD engineer to make pertinent decisions for simulation strategy, to deliver accurate and insightful results quickly for communication across the project team.

Stuart Abercrombie, Senior Engineering Consultant, Team Consulting

Correlating simulations with physical testing

Physical prototypes were tested using a next generation impactor (NGI) to measure the aerodynamic particle size distribution (APSD) of the delivered dose. The test results showed significant improvement of fine particle dose (FPD) and fine particle fraction (FPF). These results correlated with key CFD metrics of greater swirl intensity in the airflow and greater deagglomeration forces acting on the dose particles.

The new design achieved favourable flow rate independence for respirable fraction across a wide range of patient inhalation efforts from 2kPa to 6kPa pressure drop. The results across this pressure drop range demonstrated stable FPD from 39% to 40% and FPF from 52% to 57%. This demonstrates that the device is able to compensate for weak inhalation effort for patients and still maintain consistent dose delivery.


The new capsule inhaler improves the reliability of drug delivery by minimising the impact of variability across patient inhalation capabilities and techniques, drastically improving consistency of drug delivery to the deep lung. This is highly beneficial for patients to help manage their condition effectively and achieve positive therapeutic outcomes. It reduces the risk of disease exacerbations and decreases adverse side effects from drug deposition in the mouth and throat.

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