Particle Transport and Deposition under High-Frequency Oscillatory Ventilation and Normal Breathing

Figures & data

FIG. 1 The computational domain of the study. (a) A multiblock structured grid with the adoption of the “butterfly” topology representing G3–G4 bifurcation of the human lung, (b) an illustration of the internal grid.

TABLE 1 Relative square error comparison for three consecutively finer computational domains

Compared grids	ϵ rms
GI vs GII	1.15%
GII vs GIII	0.61%

FIG. 2 Contour of the dominant velocity magnitude at the plane symmetry of PBR for the HFOV case for four different time phases (a) inhalation start, (b) inhalation peak, (c) flow reversal, and (d) exhalation peak.

TABLE 2 Summary of flow characteristics for HFOV and NB cases

			Peak	Tidal
	Period	Frequency	Reynolds	volume	Womersley
Case	T(s)	f (Hz)	number	(l)	number
NB	4	0.25	1250	0.10075	0.886227
HFOV	0.0625	16	1250	0.00157422	7.08982

TABLE 3 Spherical particle diameters and Stokes number

Particle		Particle relaxation
size	Stokes number	time (s)
1 nm	7.1533 × 10^−7	6.2343 × 10^−10
50 nm	4.0785 × 10^−5	3.5545 × 10^−8
100 nm	9.3226 × 10^−5	8.1250 × 10^−8
900 nm	3.0116 × 10^−3	2.6247 × 10^−6
5 μm	8.1702 × 10^−2	7.1206 × 10^−5
10 μm	3.2188 × 10^−1	2.8053 × 10^−4

FIG. 3 Contour of the dominant velocity magnitude at the plane symmetry of PBR for the NB case for four different time phases (a) inhalation start, (b) inhalation peak, (c) flow reversal, and (d) exhalation peak.

FIG. 4 Surface streamlines and secondary velocity contour magnitudes at a plane near the exit of the G3–G4 bifurcation at the flow reversion phase for (a) HFOV and (b) NB cases.

FIG. 5 Contour of particle deposition for 900 nm particles, around the area of the carinal ridge for the HFOV case at different time phases.

FIG. 6 Contour of particle deposition for 900 nm particles, around the area of the carinal ridge for the NB case at different time phases.

FIG. 7 Contour of particle concentration (particle diameter equal to 900 nm) at the cell centre adjacent to the wall for the HFOV and the NB case at different time phases.

TABLE 4 Deposition fraction of all particle sizes used in the simulation presented for HFOV and NB cases

Particle		Normal
size	HFOV	breathing
1 nm	68.74%	61.71%
50 nm	58.94%	53.04%
100 nm	58.92%	53.04%
900 nm	58.96%	53.07%
5 μm	60.03%	54.01%
10 μm	65.66%	57.21%