(206h) Effect of Particle Shape on Deposition Behavior in Cascade Impactor

In human respiratory system, fluid behavior is complicated, and it is difficult for predicting drug particle behavior in human lung. Therefore, cascade impactors are commonly used to assess the size characteristics of aerosols experimentally. However, a lot of questions remain related to the impactor performance, including the influence of particle shape on measured size distributions. Particle shape plays a key role in determining the particle behavior in fluid because fluid drag force varied by the cross-section area of particle.

So far, drag force of irregular shape particle is calculated by the drag coefficient C_D and it was suggested by Ganser [1], Hölzer and Sommerfeld [2], Bagheri and Bonadonna [3] and so on. However, these models were applied to the straight flow and not to the complicated flow such as the cascade impactor. Therefore, irregular particles behavior for inhalation was still unknown.

To analyze the irregular particles behavior, computational fluid dynamics and discrete phase model (CFD–DPM) was used to simulate the behavior of both fluid and irregular particles. The fluid drag force of irregular particles was calculated by the suggested models. Needle shaped particles were used as irregular particles for the CFD–DPM numerical simulation. From simulated results, recirculation vortex was observed at upper stage in the cascade impactor. Because of this recirculation vortex, fine particles deposited at upper stage. Also, it was found that the aspect ratio of particles was related to deposition in cascade impactor.

References

[1] G. H. Ganser, Powder Technology, 77 (1993) 143–152.

[2] A. Hölzer and M. Sommerfeld, Powder Technol. 184 (2008) 361–365.

[3] G. Bagheri, C. Bonadonna, Powder Technol. 301 (2016) 526–544.