Deposition Fraction of Ellipsoidal Particles in a Fully Developed Laminar Pipe Flow: Application of New Correlations for Hydrodynamic Forces and Torques

2014 ◽  
Author(s):  
Mohammad Mehdi Tavakol ◽  
Omid Abouali ◽  
Mahmood Yaghoubi ◽  
Goodarz Ahmadi
Keyword(s):  
Pipe Flow ◽  
Deposition Efficiency ◽  
Hydrodynamic Forces ◽  
Transport Processes ◽  
Creeping Flow ◽  
Spherical Particles ◽  
Low Reynolds Number Flows ◽  
Ellipsoidal Particles ◽  
Deposition Fraction ◽  
Laminar Pipe Flow

The physics of transport, deposition, detachment and reentrainment re-entrainment of particles suspended in a fluid are of great interests in many practical fluid engineering problems. For spherical particles, analysis of their translational motions is sufficient for a complete description of their transport processes. Prediction of transport and deposition of non-spherical particles, however, is more complicated due to the coupling of particle translational and rotational motions. Most studies related to dispersion of ellipsoidal particles used the traditional creeping flow formulations for hydrodynamic forces and torques. These formulations are valid for very low Reynolds number flows. In this study, dispersion and deposition of ellipsoidal particles in a fully developed laminar pipe flow are analyzed numerically using new correlations for hydrodynamic forces and torques. The deposition efficiency of the ellipsoidal particles in laminar pipe flow are calculated and the results are compared with other theoretical and numerical studies and good agreement is observed.

Deposition of Ellipsoidal Fibers in Nasal Cavity: Influence of Non-Creeping Flow Conditions

2019 ◽  
Author(s):  
Mehdi Aboulhasan Tash ◽  
Mohammad Mehdi Tavakol ◽  
Omid Abouali ◽  
Goodarz Ahmadi
Keyword(s):  
Nasal Cavity ◽  
Flow Condition ◽  
Hot Spot ◽  
Hydrodynamic Forces ◽  
Physical Activities ◽  
Creeping Flow ◽  
Airflow Rate ◽  
Ansys Fluent ◽  
Aspect Ratios ◽  
Deposition Fraction

Abstract In this study, deposition fraction of ellipsoidal particles in a 3D-Model of the nasal cavity (right airway) of a 24-year-old healthy woman was simulated for laminar and turbulent inhalation flow rates. The geometry used included the main nasal cavity from the nostril to the beginning of nasopharynx and was constructed in the Ansys-ICEM software from a CT scan image. The numerical simulations of governing equations were obtained using the Ansys-Fluent software. The mean airflow was assumed to be incompressible and steady. For turbulence modeling, the Realizable k-ε model was employed and the Lagrangian trajectory analysis method was used for particle tracking. For evaluating the ellipsoidal particle motions, several user-defined functions (UDFs) were developed and linked to the discrete phase model of the Ansys-Fluent code. The developed UDFs solve for the coupled translational and rotational equations of motion for ellipsoidal fibers and also accounts for the stochastic modeling of turbulence velocity fluctuations. The hydrodynamic forces and torques were calculated based on the non-creeping formulations for various ellipsoidal fibers. Laminar flow condition was assumed for breathing rate of 5.0 lit/min for the rest or light physical activities and turbulent flow condition was assumed for airflow rate of 20 lit/min for high physical activities. To investigate the dispersion and deposition of particles in the model of the human nasal cavity, various fibers with a semi-minor axis of 1, 3, 5 and 10 μm and various aspect ratios were considered. Using the non-creeping flow formulation for hydrodynamic forces and torques, the simulation results showed slight differences in the total deposition fraction of ellipsoidal fibers compared with the corresponding creeping flow model. Small fibers deposit roughly uniformly in the nasal cavity with no hotspot region. For the large inertial fibers, however, the nasal valve is a hot spot region, where the deposition rate reaches to its peak.

Detailed Analysis of Fiber Motion in Human Nasal Airways

2021 ◽  
Author(s):  
Jiang Li ◽  
J. W. Ma ◽  
J. Y. Tu ◽  
L. Tian ◽  
G. Ahmadi
Keyword(s):  
Experimental Data ◽  
Nasal Cavity ◽  
Particle Transport ◽  
Particle Deposition ◽  
Deposition Efficiency ◽  
Spherical Particles ◽  
Nasal Airways ◽  
Deposition Fraction ◽  
Simulation Results ◽  
Fiber Transport

Abstract Information on the fiber particle transport and deposition in human nasal airways is of great importance in inhalation toxicology study. Due to the complex interactions between the inhaled aerosol particles and human respiratory airways, the particles’ toxicity varies with their chemical composition, size, and shape. In the earlier computational study of fiber particle motion in human nasal cavities, overall deposition efficiency curves were evaluated and compared with the available experimental data. The majority of investigations were on micron-scale fiber particles, and the observed deposition fraction is strongly affected by fiber inertial impaction and the geometry of the cavity. The fiber characterization by its equivalent spheres is still not entirely fully understood. Limited existing evidence indicated that, when benchmarked by the impaction parameter, spherical particles tend to have a higher deposition fraction than that of the elongated fiber particles in the nasal cavity. More data is needed to elaborate on these observations and reveal the underlying physics. A more profound understanding of fiber transport in human airways may be obtained by comparing the fibrous particle deposition to that of the spherical particles. In this study, simulations of transport and deposition of elongated particles in a realistic human nasal cavity model for a steady laminar airflow rate were performed. FLUENT 19.2 was used to solve the airflow conditions. The elongated ellipsoidal particle transport and deposition were simulated using the coupled translational and rotational equations of motion. The hydrodynamic drag and torque, shear-induced lift, and gravitational force were included in the analysis. One-way coupling was assumed, and an in-house User Defined Function (UDF) was developed and was implemented into the ANSYS-FLUENT code for analyzing the fiber transport and deposition. The airflow field, the particle deposition efficiency, particle deposition pattern, and single-particle trajectories of fiber and sphere were analyzed and presented. The simulation results were compared with available experimental data and simulation results in the literature.

Skin Friction in Unsteady Laminar Pipe Flow

1976 ◽  
Vol 102 (1) ◽  
pp. 41-56
Author(s):  
Mario F. Letelier S. ◽  
Hans J. Leutheusser
Keyword(s):  
Skin Friction ◽  
Pipe Flow ◽  
Laminar Pipe Flow

Assessment of regional deposition of inhaled particles in human lungs by serial bolus delivery method

1996 ◽  
Vol 81 (5) ◽  
pp. 2203-2213 ◽  
Author(s):  
Chong S. Kim ◽  
S. C. Hu ◽  
P. Dewitt ◽  
T. R. Gerrity
Keyword(s):  
Particle Diameter ◽  
Deposition Efficiency ◽  
Dead Volume ◽  
Delivery Method ◽  
Constant Flow Rate ◽  
Inhaled Particles ◽  
Human Lungs ◽  
Regional Deposition ◽  
Delivery Technique ◽  
Deposition Fraction

Kim, Chong S., S. C. Hu, P. DeWitt, and T. R. Gerrity.Assessment of regional deposition of inhaled particles in human lungs by serial bolus delivery method. J. Appl. Physiol. 81(5): 2203–2213, 1996.—Detailed regional deposition of inhaled particles was investigated in young adults ( n = 11) by use of a serial bolus aerosol delivery technique. A small bolus (45 ml half-width) of monodisperse aerosols [1-, 3-, and 5-μm particle diameter ( D p)] was delivered sequentially to a specific volumetric depth of the lung (100–500 ml in 50-ml increments), while the subject inhaled clean air via a laser aerosol photometer (25-ml dead volume) with a constant flow rate (Q˙ = 150, 250, and 500 ml/s) and exhaled with the same Q˙ without a pause to the residual volume. Deposition efficiency (LDE) and deposition fraction in 10 local volumetric regions and total deposition fraction of the lung were obtained. LDE increased monotonically with increasing lung depth for all three D p. LDE was greater with smaller Q˙ values in all lung regions. Deposition was distributed fairly evenly throughout the lung regions with a tendency for an enhancement in the distal lung regions for D p = 1 μm. Deposition distribution was highly uneven for D p = 3 and 5 μm, and the region of the peak deposition shifted toward the proximal regions with increasing D p. Surface dose was 1–5 times greater in the small airway regions and 2–17 times greater in the large airway regions than in the alveolar regions. The results suggest that local or regional enhancement of deposition occurs in healthy subjects and that the local enhancement can be an important factor in health risk assessment of inhaled particles.

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