Research Papers: Multiphase Flows

Numerical Analysis of Carrier Particle Motion in a Dry Powder Inhaler

[+] Author and Article Information
Martin Sommerfeld

Zentrum für Ingenieurwissenschaften,
Martin-Luther-Universität Halle-Wittenberg,
Halle (Saale) D-06099, Germany
e-mail: martin.sommerfeld@iw.uni-halle.de

Silvio Schmalfuß

Zentrum für Ingenieurwissenschaften,
Martin-Luther-Universität Halle-Wittenberg,
Halle (Saale) D-06099, Germany
e-mail: silvio.schmalfuss@iw.uni-halle.de

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received March 18, 2015; final manuscript received July 22, 2015; published online December 8, 2015. Assoc. Editor: E. E. Michaelides.

J. Fluids Eng 138(4), 041308 (Dec 08, 2015) (12 pages) Paper No: FE-15-1185; doi: 10.1115/1.4031693 History: Received March 18, 2015; Revised July 22, 2015

The efficiency of dry powder inhalers (DPIs) for drug delivery is still very low and is therefore the objective of intensive research. Thus, numerical calculations (computational fluid dynamics (CFD)) using the Euler/Lagrange approach without coupling are being performed in order to analyze flow structure and carrier particle motion within a typical inhaler device. These computations are being performed for a steady-state situation with a flow rate of 100 l/min. Essential for the detachment of the very fine drug powder (i.e., between 1 and 5 μm) from the carrier particles are the fluid stresses experienced by such particles (i.e., relative velocity, turbulence, and fluid shear) as well as wall collisions, which are both evaluated in the present study. Since the carrier particles are rather large (i.e., normally 50–100 μm), first the importance of different relevant fluid forces, especially transverse lift forces, is investigated. Moreover, the significance of the parameters in the particle–wall collision model is highlighted and a statistical analysis of particle–wall collisions in an inhaler is conducted. The improved understanding of particle motion in the normally very complex flows of inhalers will be the basis for optimizing inhaler design.

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Fig. 1

Geometry of a typical swirl-flow inhaler device (left) (Reproduced with permission from Donovan et al. [9]. © 2011 by Wiley Periodicals, Inc.) and numerical grid used for the inhaler discretization (right).

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Fig. 2

Initial locations of the injected particles (white points) in the capsule reservoir of the inhaler (a) and Rosin–Rammler (RR) cumulative size distribution of 500 μm particles (b)

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Fig. 8

Correlation between relative velocity and location within the inhaler: (a) 50 μm particles and (b) 500 μm monosized (flow rate 100 l/min, all forces, e = 0.96 and μ = 0.01)

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Fig. 9

Radial profiles of (a) axial and (b) tangential particle velocity at the mouthpiece exit for 500 μm particles with RR distribution considering all forces; influence of wall collision parameters (flow rate 100 l/min, all forces)

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Fig. 3

Visualization of calculated stationary air velocity field through the inhaler: (a) total velocity modulus and velocity vectors near the inhaler wall, (b) magnitude of axial air velocity, (c) magnitude of tangential air velocity (color scales: magnitude of velocity in m/s), and (d) turbulent kinetic energy (color scale: m2/s2) (flow rate 100 l/min)

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Fig. 4

Calculated representative particle trajectories for monosized particles through the inhaler: upper row: particle trajectories in the entire inhaler, swirl chamber, and mouthpiece; and lower row: cross-sectional view of particle trajectories only in the mouthpiece (a) 50 μm, (b) 110 μm, and (c) 500 μm (100 l/min, all forces, e = 0.96 and μ = 0.01)

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Fig. 5

Radial profiles of particle axial velocity at the mouthpiece exit for different combinations of forces (a), influence of considered fluid dynamic forces on the residence-time distribution of the particles (b), and PDFs of instantaneous relative velocity for all particles moving through the entire inhaler (c) (flow rate 100 l/min, 500 μm particles with RR distribution, e = 0.96 and μ = 0.01)

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Fig. 6

Radial profiles of particle velocity at the mouthpiece exit for monosized 110 μm particles, influence of fluid dynamic forces (flow rate 100 l/min, e = 0.96, and μ = 0.01)

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Fig. 7

Influence of particle size on their behavior in the inhaler: (a) axial particle velocity profiles at the mouthpiece exit, (b) residence-time distribution of the particles, (c) the instantaneous relative velocity of the particle, (d) mean shear rate of the particle, and (e) turbulent kinetic energy experienced by the particles (flow rate 100 l/min, all forces, e = 0.96 and μ = 0.01)

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Fig. 10

Influence of wall collision parameters (i.e., restitution coefficient e and wall friction coefficient μ) on wall collision behavior of 500 μm particles with RR size distribution: (a) PDFs of wall-impact locations and (b) PDFs of modulus of particle wall-impact velocity (flow rate 100 l/min, all forces)

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Fig. 11

Influence of considered forces on wall collision behavior for the 110 μm particles: (a) PDFs of wall-impact locations and (b) PDFs of modulus of particle wall-impact velocity (flow rate 100 l/min, e = 0.96, and μ = 0.01)

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Fig. 12

Influence of particle size (monosized) on wall collision behavior: (a) PDFs of wall-impact locations, (b) PDFs of modulus of particle wall-impact velocity, and (c) PDFs of particle–wall impact angle measured between wall and particle trajectory (flow rate 100 l/min, all forces, e = 0.96 and μ = 0.01)

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Fig. 13

Correlation between the modulus of the instantaneous particle–wall impact velocity and axial location within the inhaler for small and large monosized particles: (a) 50 μm and (b) 500 μm (flow rate 100 l/min, all forces, e = 0.96 and μ = 0.01)




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