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Turbulence kinetic energy across the center plane of a
grid aperture at 140 L/min: (a) 1999 μm; and
(b) 532 μm grid aperture size (reprinted from Wong
et al., 2011b; with permission from John Wiley & Sons)
Figure 7.7
agglomerates impact upon the grid structure with greater force, and are
re-entrained into higher velocity fl ow fi elds, thus encountering stronger
turbulent shear fl ow. The authors emphasized the importance of the
optimal balance between aperture size, wire diameter, and grid void
percentage, in order to achieve effi cient break-up and aerosolization.
Donovan et al. (2012) investigated the infl uence of device design, size,
and morphology of carrier particles on performance of the carrier-based
DPI system. Carrier particle trajectories were modeled with CFD and the
results were compared with those obtained by
in vitro
drug deposition
studies. Two commercial DPIs with different geometries were used in the
study: the Aerolizer
®
(Plastiape S.p.A., Italy) and the Handihaler
®
(Boehringer Ingelheim Inc., USA). Distinct differences in velocity profi les
and particle trajectories (Figure 7.8) within the two inhalers were
observed. It was found that fl uid fl ow within the Aerolizer
®
promotes
particle collisions with the inhaler wall and swirling particle motion inside
the mouthpiece. However, collisions are less frequent in the Handihaler,
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