Air Flow and Particle Deposition Patterns in Bronchial Airway Bifurcations: The Effect of Different CFD Models and Bifurcation Geometries

The flow theory and air flow structures in symmetric double-bifurcation airway models assuming steady laminar, incompressible flow, unaffected by the presence of aerosols, has been described in a companion paper (Part 1). The validated computer simulation results showed highly vortical flow fields, especially around the second bifurcations, indicating potentially complex particle distributions and deposition patterns. In this paper (Part 2), assuming spherical non-interacting aerosols that stick to the wall when touching the surface, the history of depositing particles is described. Specifically, the finite-volume code CFX (AEA Technology) with user-enhanced FORTRAN programs were validated with experimental data of particle deposition efficiencies as a function of the Stokes number for planar single and double bifurcations. The resulting deposition patterns, particle distributions, trajectories and time evolution were analysed in the light of the air flow structures for relatively low (ReD1 = 500) and high (ReD1 = 2000) Reynolds numbers and representative Stokes numbers, i.e. StD1 = 0.04 and StD1 = 0.12. Particle deposition patterns and surface concentrations are largely a function of the local Stokes number, but they also depend on the fluid–particle inlet conditions as well as airway geometry factors. While particles introduced at low inlet Reynolds numbers (e.g. ReD1 = 500) follow the axial air flow, secondary and vortical flows become important at higher Reynolds numbers, causing the formation of particle-free zones near the tube centres and subsequently elevated particle concentrations near the walls. Sharp or mildly rounded carinal ridges have little effect on the deposition efficiencies but may influence local deposition patterns. In contrast, more drastic geometric changes to the basic double-bifurcation model, e.g. the 90°-non-planar configuration, alter both the aerosol wall distributions and surface concentrations considerably.

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Flow structures and particle deposition patterns in double-bifurcation airway models. Part 1. Air flow fields

Journal of Fluid Mechanics ◽

10.1017/s0022112001003809 ◽

2001 ◽

Vol 435 ◽

pp. 25-54 ◽

Cited By ~ 130

Author(s):

J. K. COMER ◽

C. KLEINSTREUER ◽

Z. ZHANG

Keyword(s):

Particle Deposition ◽

Transfer Functions ◽

Air Flow ◽

Flow Fields ◽

Companion Paper ◽

Theory Model ◽

Flow Structures ◽

Viscous Effects ◽

Number Range ◽

Deposition Patterns

The understanding and quantitative assessment of air flow fields and local micron-particle wall concentrations in tracheobronchial airways are very important for estimating the health risks of inhaled particulate pollutants, developing algebraic transfer functions of global lung deposition models used in dose-response analyses, and/or determining proper drug-aerosol delivery to target sites in the lung. In this paper (Part 1) the theory, model geometries, and air flow results are provided. In a companion paper (Part 2, Comer et al. 2001), the history of particle deposition patterns and comparisons with measured data sets are reported. Decoupling of the naturally dilute particle suspension makes it feasible to present the results in two parts.Considering a Reynolds number range of 500 [les ] ReD [les ] 2000, it is assumed that the air flow is steady, incompressible and laminar and that the tubular double bifurcations, i.e. Weibel's generations G3–G5, are three-dimensional, rigid, and smooth with rounded as well as sharp carinal ridges for symmetric planar, and just rounded carinas for 90° non-planar configurations. The employed finite-volume code CFX (AEA Technology) and its user-enhanced FORTRAN programs were validated with experimental velocity data points for a single bifurcation. The resulting air flow structures are analysed for relatively low (ReD = 500) and high (ReD = 2000) Reynolds numbers. Sequential pressure drops due to viscous effects were calculated and compared, extending a method proposed by Pedley et al. (1977). Such detailed results for bifurcating lung airways are most useful in the development of global algebraic lung models.

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Particle Deposition Characteristics and Efficiency in Duct Air Flow over a Backward-Facing Step: Analysis of Influencing Factors

Sustainability ◽

10.3390/su11030751 ◽

2019 ◽

Vol 11 (3) ◽

pp. 751

Author(s):

Hao Lu ◽

Li-zhi Zhang

Keyword(s):

Particle Deposition ◽

Air Flow ◽

Deposition Velocity ◽

Particle Diameter ◽

Deposition Efficiency ◽

Reynolds Stress Model ◽

Expansion Ratio ◽

Particle Model ◽

Duct Flow ◽

Backward Facing Step

Dry deposition of airborne particles in duct air flow over a backward-facing step (BFS) is commonly encountered in built environments and energy engineering. However, the understanding of particle deposition characteristics in BFS flow remains insufficient. Thus, this study investigated particle deposition behaviors and efficiency in BFS flow by using the Reynolds stress model and the discrete particle model. The influences of flow velocities, particle diameters, and duct expansion ratios on particle deposition characteristics were examined and analyzed. After numerical validation, particle deposition velocities, deposition efficiency, and deposition mechanisms in BFS duct flow were investigated in detail. The results showed that deposition velocity in BFS duct flow monotonically increases when particle diameter increases. Moreover, deposition velocity falls with increasing expansion ratio but rises with increasing air velocity. Deposition efficiency, the ratio of deposition velocity, and flow drag in a BFS duct is higher for small particles but lower for large particles as compared with a uniform duct. A higher particle deposition efficiency can be achieved by BFS with a smaller expansion ratio. The peak deposition efficiency can reach 33.6 times higher for 1-μm particles when the BFS expansion ratio is 4:3. Moreover, the “particle free zone” occurs for 50-μm particles in the BFS duct and is enlarged when the duct expansion ratio increases.

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Comparison of Micron and Nano Particle Deposition Patterns in a Realistic Human Nasal Cavity

IFMBE Proceedings - 13th International Conference on Biomedical Engineering ◽

10.1007/978-3-540-92841-6_384 ◽

2009 ◽

pp. 1550-1554

Author(s):

K. Inthavong ◽

S. M. Wang ◽

J. Wen ◽

J. Y. Tu ◽

C. L. Xue

Keyword(s):

Nasal Cavity ◽

Particle Deposition ◽

Nano Particle ◽

Deposition Patterns

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Investigation of particle deposition efficiency enhancement in turbulent duct air flow by surface ribs with hybrid-size ribs

Indoor and Built Environment ◽

10.1177/1420326x16662509 ◽

2016 ◽

Vol 26 (5) ◽

pp. 608-620 ◽

Cited By ~ 2

Author(s):

Hao Lu ◽

Lin Lu

Keyword(s):

Particle Deposition ◽

Air Flow ◽

Deposition Efficiency ◽

Dynamics Simulation ◽

Particle Model ◽

Particle Removal ◽

Cleaning Equipment ◽

Discrete Particle Model ◽

Turbulent Air Flow ◽

Flow Drag

This study presents the particle deposition enhancement by hybrid-size and same-size surface ribs in turbulent air duct flows using computational fluid dynamics simulation. The Reynolds stress turbulence model with UDF corrections and discrete particle model were adopted to simulate the turbulent air flow fields and particle deposition behaviours, respectively. After numerical validation with the relative literature results, pure particle deposition enhancement ratios, flow drag increase, comprehensive deposition efficiency and deposition enhancement mechanisms were investigated and discussed in details. The findings showed that the hybrid-size ribs with small rib spacing have the best enhancement performance on particle deposition for small particles ([Formula: see text]). Considering the flow drag increase, the maximum deposition efficiency can reach 485 for 1 µm particles for the hybrid-size ribbed cases, while it is just 425 for the same-size ribbed case. Nevertheless, no obvious particle deposition enhancement can be found for large particles ([Formula: see text]) for all types of surface ribs. The hybrid-size surface ribs are more efficient compared with the same-size ribs, which can be applied in the air cleaning equipment to improve the aerosol particle removal performance.

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Comparison Between the Numerical and Experimental Deposition Patterns for an Electrostatic Rotary Bell Sprayer

Volume 2B: Advanced Manufacturing ◽

10.1115/imece2015-50211 ◽

2015 ◽

Cited By ~ 3

Author(s):

Husam Osman ◽

Kazimierz Adamiak ◽

G. S. Peter Castle ◽

Hua-Tzu (Charles) Fan ◽

Joseph Simmer

Keyword(s):

Numerical Model ◽

Mass Flow Rate ◽

Flow Rate ◽

Particle Deposition ◽

Numerical Results ◽

Deposition Patterns ◽

Dispersed Particles ◽

3D Numerical Model ◽

Deposition Thickness ◽

Fractional Mass

In this paper, a full 3D numerical model using ANSYS commercial software has been created to simulate the particle deposition profile for stationary and moving flat targets, assuming multiple injections of charged poly-dispersed particles. Different injection angles along three virtual rings were assumed to form a shower injection pattern. The experimental and the numerical results of deposition thickness have been presented and compared for different injection patterns. It has been found that there are some parameters, such as the total number of injection points, the radii of the rings and the fractional mass flow rate in each injection ring, which affect the numerical results of the deposition thickness and uniformity.

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29.P.18 Comparison of particle deposition patterns in human and rat lungs

Journal of Aerosol Science ◽

10.1016/0021-8502(94)90482-0 ◽

1994 ◽

Vol 25 ◽

pp. 505-506

Author(s):

Werner Hofmann ◽

László Koblinger

Keyword(s):

Particle Deposition ◽

Deposition Patterns ◽

Rat Lungs

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Particle Deposition Onto a Flat Surface from a Point Particle Source

Journal of the IEST ◽

10.17764/jiet.1.31.6.n65256516m648901 ◽

1988 ◽

Vol 31 (6) ◽

pp. 39-41

Author(s):

Frank Stratmann ◽

Heinz Fissan ◽

Thomas Peterson

Keyword(s):

Particle Deposition ◽

Flat Surface ◽

Particle Beam ◽

Point Particle ◽

Two Dimensional ◽

Stagnation Flow ◽

Flow Configuration ◽

Convection Diffusion ◽

Deposition Patterns ◽

Thermophoresis Particle Deposition

A series of two-dimensional calculations are performed to determine particle fluxes to wafers in a stagnation flow configuration. Mechanisms that influenced particle deposition included convection, diffusion, sedimentation, and thermophoresis. Particle deposition patterns resulting from a uniform freestream concentration are compared with deposition patterns from a narrow particle beam.

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