Aerosol Transport and Deposition in Sequentially Bifurcating Airways

1999 ◽  
Vol 122 (2) ◽  
pp. 152-158 ◽  
Author(s):  
J. K. Comer ◽  
C. Kleinstreuer ◽  
S. Hyun ◽  
C. S. Kim
Keyword(s):  
Particle Deposition ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Deposition Efficiency ◽  
Stokes Number ◽  
Direct Result ◽  
Constant Property ◽  
Deposition Patterns ◽  
Inhaled Particles ◽  
Out Of Plane

Deposition patterns and efficiencies of a dilute suspension of inhaled particles in three-dimensional double bifurcating airway models for both in-plane and 90 deg out-of-plane configurations have been numerically simulated assuming steady, laminar, constant-property air flow with symmetry about the first bifurcation. Particle diameters of 3, 5, and 7 μm were used in the simulation, while the inlet Stokes and Reynolds numbers varied from 0.037 to 0.23 and 500 to 2000, respectively. Comparisons between these results and experimental data based on the same geometric configuration showed good agreement. The overall trend of the particle deposition efficiency, i.e., an exponential increase with Stokes number, was somewhat similar for all bifurcations. However, the deposition efficiency of the first bifurcation was always larger than that of the second bifurcation, while in general the particle efficiency of the out-of-plane configuration was larger than that of the in-plane configuration. The local deposition patterns consistently showed that the majority of the deposition occurred in the carinal region. The distribution pattern in the first bifurcation for both configurations were symmetric about the carina, which was a direct result of the uniaxial flow at the inlet. The deposition patterns about the second carina showed increased asymmetry due to highly nonuniform flow generated by the first bifurcation and were extremely sensitive to bifurcation orientation. Based on the deposition variations between bifurcation levels and orientations, the use of single bifurcation models was determined to be inadequate to resolve the complex fluid–particle interactions that occur in multigenerational airways. [S0148-0731(00)01102-X]

Flow structures and particle deposition patterns in double-bifurcation airway models. Part 2. Aerosol transport and deposition

2001 ◽  
Vol 435 ◽  
pp. 55-80 ◽  
Author(s):  
J. K. COMER ◽  
C. KLEINSTREUER ◽  
C. S. KIM
Keyword(s):  
Particle Deposition ◽  
Air Flow ◽  
Reynolds Numbers ◽  
Companion Paper ◽  
Stokes Number ◽  
Vortical Flow ◽  
Flow Structures ◽  
Particle Distributions ◽  
Deposition Patterns ◽  
Inlet Conditions

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.

Local particle deposition patterns may play a key role in the development of lung cancer

2003 ◽  
Vol 94 (5) ◽  
pp. 1719-1725 ◽  
Author(s):  
Imre Balásházy ◽  
Werner Hofmann ◽  
Thomas Heistracher
Keyword(s):  
Lung Cancer ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Average Dose ◽  
Deposition Patterns ◽  
Cancer Induction ◽  
Inhaled Particles ◽  
Site Selectivity ◽  
Enhancement Factors ◽  
Neoplastic Lesions

The apparent discrepancy between the reported preferential occurrence of bronchial carcinomas in central bronchial airways and current dose estimates for inhaled particles suggests that experimentally observed local accumulations of particles within bronchial airway bifurcations may play a crucial role in lung cancer induction. Here, we computed three-dimensional particle deposition patterns in lobar-segmental airway bifurcations and quantified the resulting inhomogeneous deposition patterns in terms of deposition enhancement factors, which are defined as the ratio of local to average deposition densities. Our results revealed that a small fraction of epithelial cells located at carinal ridges can receive massive doses that may be even a few hundred times higher than the average dose for the whole airway. This lends further credence to the hypothesis that the apparent site selectivity of neoplastic lesions may indeed be caused by the enhanced deposition of toxic particulate matter at bronchial airway bifurcations.

Simulation of three-dimensional particle deposition patterns

1998 ◽  
Vol 29 ◽  
pp. S947-S948 ◽  
Author(s):  
R. Bergmann ◽  
W. Hofmann ◽  
J.S. Fleming ◽  
J.H. Conway
Keyword(s):  
Particle Deposition ◽  
Three Dimensional ◽  
Deposition Patterns

Simulation of Three-Dimensional Particle Deposition Patterns in Human Lungs and Comparison with Experimental SPECT Data

2005 ◽  
Vol 39 (8) ◽  
pp. 771-781 ◽  
Author(s):  
W. Hofmann ◽  
L. Bolt ◽  
R. Sturm ◽  
J. S. Fleming ◽  
J. H. Conway
Keyword(s):  
Particle Deposition ◽  
Three Dimensional ◽  
Deposition Patterns ◽  
Human Lungs

Pressure and Temperature Effects on Particle Deposition in an Impinging Flow

2017 ◽  
Author(s):  
Ryan K. Lundgreen
Keyword(s):  
Reynolds Number ◽  
Particle Deposition ◽  
Stokes Equations ◽  
Focal Point ◽  
Three Dimensional ◽  
Stokes Number ◽  
Particle Impact ◽  
Internal Cooling ◽  
Particle Reynolds Number ◽  
Impinging Flow

Particle deposition is a significant problem in gas turbine engines. Internal cooling passages are of particular interest because deposition build up is observed at far lower temperatures than it is for external flows. Computational fluid dynamics were employed to investigate how changes in the particle Reynolds number affected deposition in an impinging flow. Three-dimensional, steady Reynolds-Averaged Navier-Stokes equations were solved for a single impinging jet that had a jet to wall spacing of H/D = 2. Pressure ratios of 1.015 and 1.03 were considered at three different discharge pressures, 0.1, 1 , and 3 MPa. Three different flow temperatures were also considered, 300, 700, and 1000 K. Five different particle diameters ranging from 0.5 – 10 μm were tracked in each solution. The aerodynamic lensing focal point of the particle tracks, particle impact velocities, particle impact angles, and particle impact locations were all characterized well by the effective Stokes number. The effective Stokes number adjusts the Stokes number by the non-Stokes drag correction factor, which is a function of the particle Reynolds number.

Flow and Deposition Characteristics Following Chokes for Pressurized CO2 Pipelines

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Lin Teng ◽  
Yuxing Li ◽  
Hui Han ◽  
Pengfei Zhao ◽  
Datong Zhang
Keyword(s):  
Particle Size ◽  
Flow Velocity ◽  
Particle Deposition ◽  
Transport Model ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Stokes Number ◽  
Sudden Expansion ◽  
Tracking Model ◽  
Good Agreement

The relieving system using the choke valve is applied to control the pressure in CO2 pipeline. However, the temperature of fluid would drop rapidly because of Joule–Thomson cooling (JTC), which may cause solid CO2 form and block the pipe. A three-dimensional (3D) computational fluid dynamic (CFD) model considering the phase transition and turbulence was developed to predict the fluid-particle flow and deposition characteristics. The Lagrangian method, Reynold's stress transport model (RSM) for turbulence, and stochastic tracking model (STM) were used. The results show that the model predictions were in good agreement with the experimental data published. The effects of particle size, flow velocity, and pipeline diameter were analyzed. It was found that the increase of the flow velocity would cause the decrease of particle deposition ratio and there existed the critical particle size that causes the deposition ratio maximum. It also presents the four types of particle motions corresponding to the four deposition regions. Moreover, the sudden expansion region is the easiest to be blocked by the particles. In addition, the Stokes number had an effect on the deposition ratio and it was recommended for Stokes number to avoid 3–8 St.

scholarly journals STUDY OF CALCITE PRECIPITATION IN WELL CONDITIONS USING THE DDPM-DPM APPROACH

2021 ◽  
Vol 51 (2) ◽  
pp. 101-106
Author(s):  
Suellen Freire Rigatto da Cruz ◽  
Fabio De Assis Ressel Pereira ◽  
Daniel Da Cunha Ribeiro ◽  
André Leibsohn Martins ◽  
Oldrich Joel Romero
Keyword(s):  
Particle Deposition ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Computational Effort ◽  
Scale Formation ◽  
Discrete Phase Model ◽  
Calcite Precipitation ◽  
Discrete Phase ◽  
It Application ◽  
Calcium Carbonate Scale

The extraction of oil results in problems such as the scale formation in the various stages of the production process. The scale reduces all or part of the flow conduits, increasing the pressure drop and reducing oil production. In this work the three dimensional, transient, turbulent, biphasic problem is solved by combining the Dense Discrete Phase Model (DDPM) and Discrete Element Method (DEM), to analyze the influence of certain parameters on the particle deposition, which represents the calcium carbonate scale formation, inside the wall of a horizontal pipeline at well conditions. The obtained results show that particle deposition is higher at lower Reynolds numbers. The results also show that the use of DEM model is more representative, but due to the high computational effort required, it application in complex geometries must be carefully evaluated.

3D simulation of emulsion flow using the boundary element method on the heterogeneous computational systems

2012 ◽  
Vol 9 (1) ◽  
pp. 142-146
Author(s):  
O.A. Solnyshkina
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Problem Size ◽  
Low Reynolds Numbers ◽  
Infinite Domains ◽  
The Matrix ◽  
Computational Systems ◽  
Element Method

In this work the 3D dynamics of two immiscible liquids in unbounded domain at low Reynolds numbers is considered. The numerical method is based on the boundary element method, which is very efficient for simulation of the three-dimensional problems in infinite domains. To accelerate calculations and increase the problem size, a heterogeneous approach to parallelization of the computations on the central (CPU) and graphics (GPU) processors is applied. To accelerate the iterative solver (GMRES) and overcome the limitations associated with the size of the memory of the computation system, the software component of the matrix-vector product

scholarly journals A Numerical Study of the Effect of Particle Size on Particle Deposition on Turbine Vanes and Blades

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110178
Author(s):  
Zhengang Liu ◽  
Weinan Diao ◽  
Zhenxia Liu ◽  
Fei Zhang
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Numerical Study ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Factors Affecting ◽  
Pressure Surface ◽  
Deposition Area ◽  
Turbine Vanes

Particle deposition could decrease the aerodynamic performance and cooling efficiency of turbine vanes and blades. The particle motion in the flow and its temperature are two important factors affecting its deposition. The size of the particle influences both its motion and temperature. In this study, the motion of particles with the sizes from 1 to 20 μm in the first stage of a turbine are firstly numerically simulated with the steady method, then the particle deposition on the vanes and blades are numerically simulated with the unsteady method based on the critical viscosity model. It is discovered that the particle deposition on vanes mainly formed near the leading and trailing edge on the pressure surface, and the deposition area expands slowly to the whole pressure surface with the particle size increasing. For the particle deposition on blades, the deposition area moves from the entire pressure surface toward the tip with the particle size increasing due to the effect of rotation. For vanes, the particle capture efficiency increases with the particle size increasing since Stokes number and temperature of the particle both increase with its size. For blades, the particle capture efficiency increases firstly and then decreases with the particle size increasing.

Turbulent three-dimensional dielectric electrohydrodynamic convection between two plates

2012 ◽  
Vol 696 ◽  
pp. 228-262 ◽  
Author(s):  
A. Kourmatzis ◽  
J. S. Shrimpton
Keyword(s):  
Spatial Data ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Energy Budgets ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Wide Range ◽  
Scalar Variance

AbstractThe fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low (${\mathit{Re}}_{E} = 1$) and high electric Reynolds numbers (up to ${\mathit{Re}}_{E} = 120$). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\ensuremath{\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\ensuremath{\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC; however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.

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