| In MDIs, the drug is stored in pressurized liquid
propellant suspension. Upon actuation, flash atomization of the propellant
results in a drug particle containing aerosol spray, which is then transported
to the deep lung via inhalation. CFDRC engineers have developed the technology
to guide the design of a MDI device by assessing aerosol plume transport
(reducing deposition and improving delivery characteristics).
For instance, we assess the influence of a makeup air inlet geometry
in a hypothetical MDI device in this example. In simulation 1, the make-up
air stream flows in parallel to the propellant (and drug) injection, whereas
air is introduced into the device in an annular fashion in the second
simulation. Instead of the anticipated "sheath" formation at
the walls and subsequent reduction in deposition, annular air stream results
in the formation of strong shear layers, which adversely impact aerosol
plume dispersion.
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