Modeling Of Aerosol Deposition Research Articles

Simplified models of aerosol collision and deposition for disease transmission

Fluid-mechanics research has focused primarily on droplets/aerosols being expelled from infected individuals and transmission of well-mixed aerosols indoors. However, aerosol collisions with susceptible hosts earlier in the spread, as well as aerosol deposition in the nasal cavity, have been relatively overlooked. In this paper, two simple fluid models are presented to gain a better understanding of the collision and deposition between a human and aerosols. The first model is based on the impact of turbulent diffusion coefficients and air flow in a room on the collisions between aerosols and humans. Infection rates can be determined based on factors such as air circulation and geometry as an infection zone expands from an infected host. The second model clarifies how aerosols of different sizes adhere to different parts of the respiratory tract. Based on the inhalation rate and the nasal cavity shape, the critical particle size and the deposition location can be determined. Our study offers simple fluid models to understand the effects of geometric factors and air flows on the aerosol transmission and deposition.

Study of poly-disperse aerosols deposition in turbulent flow with different Reynolds numbers

The turbulent deposition mechanism is one of the main mechanisms of aerosol deposition in nuclear power plant tubes. An experimental study of poly-disperse aerosol deposition in a horizontal tube is conducted, where the nominal Reynolds number (Re) is in a range of 3600–200,000. The aerosol deposition velocity first increases and then decreases with the increase of Res, and at high Re, particle rebound occurs during aerosol deposition in the tube. When the Re is low, the aerosol deposition velocity increases with the increase of aerosol diameter. When the Re is greater than 60,000, the deposition velocity first increases and then decreases with the increase of aerosol diameter due to particle surface rebound. A new aerosol deposition model has been developed by establishing the energy conservation equation of the rebounded particles in the viscous sublayer. The calculated results of the new model are in good agreement with these experimental results, and the error between the aerosol deposition velocity calculated by the model and experimental results is between −60% and 150%.

In Silico Quantification of Intersubject Variability on Aerosol Deposition in the Oral Airway

The extrathoracic oral airway is not only a major mechanical barrier for pharmaceutical aerosols to reach the lung but also a major source of variability in lung deposition. Using computational fluid dynamics, deposition of 1−30 µm particles was predicted in 11 CT-based models of the oral airways of adults. Simulations were performed for mouth breathing during both inspiration and expiration at two steady-state flow rates representative of resting/nebulizer use (18 L/min) and of dry powder inhaler (DPI) use (45 L/min). Consistent with previous in vitro studies, there was a large intersubject variability in oral deposition. For an optimal size distribution of 1−5 µm for pharmaceutical aerosols, our data suggest that >75% of the inhaled aerosol is delivered to the intrathoracic lungs in most subjects when using a nebulizer but only in about half the subjects when using a DPI. There was no significant difference in oral deposition efficiency between inspiration and expiration, unlike subregional deposition, which shows significantly different patterns between the two breathing phases. These results highlight the need for incorporating a morphological variation of the upper airway in predictive models of aerosol deposition for accurate predictions of particle dosimetry in the intrathoracic region of the lung.

Application of an aerosol deposition model to whole body dermal exposure scenarios involving VX

In this report we present the application of a modified aerosol deposition model to a number of scenarios involving a whole body dermal exposure to the toxic chemical nerve agent VX in the form of a liquid aerosol. An aerosol deposition model is modified to simulate the distribution of deposited aerosolized particles on the surface of a mannequin exposed to a turbulent air stream with a specified aerosol concentration and particle size distribution, using as few turbulence flow parameters as possible. The aerosol deposition model allows for the calculation of deposition velocity, total deposited mass, and other quantities, over the entire surface of a mannequin given the aerosol concentration, exposure time, particle size distribution, and air flow conditions are specified. The model uses shear velocity distributions over a mannequin, obtained from computational fluid dynamic (CFD) simulations, and accounts for three particle transport mechanisms: Brownian (molecular) diffusion, turbulence (eddy) diffusion, and gravitational sedimentation. Additionally, the model considers surface roughness and orientation of the mannequin surface relative to gravity. The model is integrated into a broader computer program, written in the Fortran programming language, that handles all input and output.

A New Aerosol Dry Deposition Model for Air Quality and Climate Modeling

AbstractDry deposition of aerosols from the atmosphere is an important but poorly understood and inadequately modeled process in atmospheric systems for climate and air quality. Comparisons of currently used aerosol dry deposition models to a compendia of published field measurement studies in various landscapes show very poor agreement over a wide range of particle sizes. In this study, we develop and test a new aerosol dry deposition model that is a modification of the current model in the Community Multiscale Air Quality (CMAQ) model. The new model agrees much better with measured dry deposition velocities across particle sizes. The key innovation is the addition of a second inertial impaction term for microscale obstacles such as leaf hairs, microscale ridges, and needleleaf edge effects. The most significant effect of the new model is to increase the mass dry deposition of the accumulation mode aerosols in CMAQ. Accumulation mode mass dry deposition velocities increase by almost an order of magnitude in forested areas with lesser increases for shorter vegetation. Peak PM2.5 concentrations are reduced in some forested areas by up to 40% in CMAQ simulations. Over the continuous United States, the new model reduced PM2.5 by an average of 16% for July 2018 at the Air Quality System monitoring sites. For summer 2018 simulations, bias and error of PM2.5 concentrations are significantly reduced, especially in forested areas.

Experimental and Numerical Study on the Gravitational Deposition and Coagulation of Aerosols

The gravitational deposition and coagulation of aerosols were studied experimentally based on the COSTTHES (Containment Source-Term and Thermal Hydraulics Experiment System) facility and numerically investigated based on a continuous general dynamic equation; the experimental and the numerical results were in good agreement. In the present study, the applicability of the zero-dimensional model for deposition and coagulation of aerosols was verified. A considerable distortion can occur due to the coagulation of the aerosol, which significantly influenced the removal rate of the aerosol with a diameter greater than 0.76 µm, and the dynamic shape factor value of the aerosol used in the present experiment was obtained as 4. In the experimental and numerical studies, it was found that the combined effect of the gravitational deposition and coagulation of the aerosol can increase the number density of the aerosol with specific diameters, and the concentration-increment size would increase as settling continued.

Characterizing the Effects of Nasal Prong Interfaces on Aerosol Deposition in a Preterm Infant Nasal Model

The objective of this study was to characterize the effects of multiple nasal prong interface configurations on nasal depositional loss of pharmaceutical aerosols in a preterm infant nose-throat (NT) airway model. Benchmark in vitro experiments were performed in which a spray-dried powder formulation was delivered to a new preterm NT model with a positive-pressure infant air-jet dry powder inhaler using single- and dual-prong interfaces. These results were used to develop and validate a computational fluid dynamics (CFD) model of aerosol transport and deposition in the NT geometry. The validated CFD model was then used to explore the NT depositional characteristic of multiple prong types and configurations. The CFD model highlighted a turbulent jet effect emanating from the prong(s). Analysis of NT aerosol deposition efficiency curves for a characteristic particle size and delivery flowrate (3 µm and 1.4 L/min (LPM)) revealed little difference in NT aerosol deposition fraction (DF) across the prong insertion depths of 2–5 mm (DF = 16–24%) with the exception of a single prong with 5-mm insertion (DF = 36%). Dual prongs provided a modest reduction in deposition vs. a single aerosol delivery prong at the same flow for insertion depths < 5 mm. The presence of the prongs increased nasal depositional loss by absolute differences in the range of 20–70% compared with existing correlations for ambient aerosols. In conclusion, the use of nasal prongs was shown to have a significant impact on infant NT aerosol depositional loss prompting the need for prong design alterations to improve lung delivery efficiency.Graphical

Assessment of the predictive capability of modelling and simulation to determine bioequivalence of inhaled drugs: A systematic review.

There are a multitude of different modelling techniques that have been used for inhaled drugs. The main objective of this review was to conduct an exhaustive survey of published mathematical models in the area of asthma and chronic obstructive pulmonary disease (COPD) for inhalation drugs. Additionally, this review will attempt to assess the applicability of these models to assess bioequivalence (BE) of orally inhaled products (OIPs). PubMed, Science Direct, Web of Science, and Scopus databases were searched from 1996 to 2020, to find studies that described mathematical models used for inhaled drugs in asthma/COPD. 50 articles were finally included in this systematic review. This research identified 22 articles on in silico aerosol deposition models, 20 articles related to population pharmacokinetics and 8 articles on physiologically based pharmacokinetic modelling (PBPK) modelling for inhaled drugs in asthma/COPD. Among all the aerosol deposition models, computational fluid dynamics (CFD) simulations are more likely to predict regional aerosol deposition pattern in human respiratory tracts. Across the population PK articles, body weight, gender, age and smoking status were the most common covariates that were found to be significant. Further, limited published PBPK models reported approximately 29 parameters relevant for absorption and distribution of inhaled drugs. The strengths and weaknesses of each modelling technique has also been reviewed. Overall, while there are different modelling techniques that have been used for inhaled drugs in asthma and COPD, there is very limited application of these models for assessment of bioequivalence of OIPs. This review also provides a ready reference of various parameters that have been considered in various models which will aid in evaluation if one model or hybrid in silico models need to be considered when assessing bioequivalence of OIPs.

Study on Aerosol Transport and Deposition Model of Ocean Air Flow

Study on Aerosol Transport and Deposition Model of Ocean Air Flow

Development of an alternative predictive model of aerosol deposition in macaque monkeys and associated means of administration

Development of an alternative predictive model of aerosol deposition in macaque monkeys and associated means of administration

Comparison of Voxel‐Based and Mesh‐Based CFD Models for Aerosol Deposition on Complex Fibrous Filters

Dennis Hoch*, Mehdi Azimian, André Baumann, Jens Behringer, Jennifer Niessner, Comparison of Voxel–Based and Mesh–Based CFD Models for Aerosol Deposition on Complex Fibrous Filters, Chem. Eng. Technol. 2020, 43 (12), 2538–2547. DOI: https://doi.org/10.1002/ceat.202000318 The GeoDict simulation (grey curve) in Fig. 2 was not correct. The correct figure should be:

Anatomical considerations for inhaled aerosol deposition modeling: Methods, applications, challenges and opportunities

This paper, one of several in a special issue of the Journal of Aerosol Science on “Inhaled Aerosol Dosimetry”, covers selected methods for defining the respiratory tract anatomy required as input to inhaled aerosol deposition models, along with some applications and challenges. “Anatomy” refers to the study of biological structures and to the structures themselves. Quantitative anatomical data obtained by morphometric measurements are used in inhaled aerosol deposition dose models. The equations used in modeling calculations define the needed specific quantitative anatomy input, whether the model is deterministic, stochastic, semi-empirical, or computational fluid dynamics based. Replica airway casts are widely used for defining airway morphology, and for making hollow models to validate deposition calculations. The parameters measured on casts, e.g., airway lengths, diameters, branching and gravity angles, alveolar shapes, and generational linkages do not capture some important airway details, such as bifurcation shapes, airway motion, deviations from airway smoothness, and non-uniform airway tube diameters. These details can affect inhaled aerosol fates. Advances in methods for scanning airways in living subjects or in non-dissected excised lungs have overcome many of the problems associated with replica cast morphometry, but limitations remain with respect to providing linked airway regions, capturing airway motion, and resolving fine structural detail. There are also needs for cast measurements and scans that represent additional animal species and normal variations within species and individuals. Other methods for defining airway anatomy, such as serial sectioning of fixed or frozen tissue, planar x-ray imaging, and bolus aerosol inhalation, also provide useful airway anatomical data. Along with advances in aerosol dynamics, the current state of understanding airway anatomy is adequate for modeling many medical and environmental exposure cases. However, it appears that advances in understanding respiratory tract anatomy and physiology have lagged behind advances in the quality of aerosol science used in current inhaled aerosol deposition models, with the exception of dynamic and/or multi-component aerosol systems (e.g., cigarette smoke). Accordingly, for anatomists and aerosol scientists working on inhaled aerosol dose models both challenges and opportunities lie ahead for addressing remaining anatomical issues of concern.

Comparison of Voxel‐Based and Mesh‐Based CFD Models for Aerosol Deposition on Complex Fibrous Filters

AbstractAerosols represent a health risk since small droplets may enter the respiratory system and cause lung cancer, allergies, or diseases like COVID‐19. In this work, an Eulerian‐Lagrangian computational fluid dynamics model is used based on a voxel‐based (GeoDict) and a mesh‐based (StarCCM+) code. For evaluating accuracy and computational time of both models, fractional filtration efficiency and pressure drop are compared to an empirical solution for a single fiber and to experimental results for a complex 3D fibrous filter material. Simulation results of both methods are in good agreement with empirical and measurement results although the complex geometry of the fibers is captured more accurately by the unstructured mesh using the same resolution. Computing times are much faster using the voxel‐based code.

FALL3D-8.0: a computational model for atmospheric transport and deposition of particles, aerosols and radionuclides – Part 1: Model physics and numerics

Abstract. This paper presents FALL3D-8.0, the last version release of an open-source code with 15+ years of track record and a growing number of users in the volcanological and atmospheric communities. The code has been redesigned and rewritten from scratch in the framework of the EU Centre of Excellence for Exascale in Solid Earth (ChEESE) in order to overcome legacy issues and allow for successive optimisations in the preparation of the code towards extreme-scale computing. However, this baseline version already contains substantial improvements in terms of model physics, solving algorithms, and code accuracy and performance. The code, originally conceived for atmospheric dispersal and deposition of tephra particles, has been extended to model other types of particles, aerosols and radionuclides. The solving strategy has also been changed, replacing the former central-difference scheme for a high-resolution central-upwind scheme derived from finite volumes, which minimises numerical diffusion even in the presence of sharp concentration gradients and discontinuities. The parallelisation strategy, input/output (I/O), model pre-process workflows and memory management have also been reconsidered, leading to substantial improvements on code scalability, efficiency and overall capability to handle much larger problems. All these new features and improvements have implications on operational model performance and allow, among others, adding data assimilation and ensemble forecast in future releases. This paper details the FALL3D-8.0 model physics and the numerical implementation of the code.

Development of mathematical model for aerosol deposition under jet condition

Gas-liquid jet flow is a typical phenomenon in severe reactor accidents. It is great significance to evaluate the scrubbing efficiency of aerosols in jet flow conditions reasonably for the analysis of source terms and also adopting mitigation measures.In this paper, a visualization experiment is carried out, and a mathematical model is developed based on the experiment results by considering the deposition mechanism from fluctuation interface and entrainment droplets simultaneously. Model verification results show that in case of gas injection flow under lower velocity, fluctuated gas-liquid interface play a dominant role on aerosol removal, but the jet flow condition has a weak filtration effect on aerosols with small particle size. While in case of high velocity, entrainment droplets may play a dominant role on aerosols removal and the scrubbing efficiency gradually loses its sensitivity to particle size and maintain upon 99%.

安全壳微小通道内气溶胶沉积模型综述

安全壳微小通道内气溶胶沉积模型综述

Eulerian modeling of aerosol transport and deposition in respiratory tract under thermodynamic equilibrium condition

A computational study is carried out using a purely Eulerian approach for investigating the inhaled e-cigarette aerosol transport and deposition in the human upper respiratory tract (URT). These aerosols consist of some volatile compounds and are generally hygroscopic with vapor liquid phase change at the particle–air interface. An Eulerian model is developed based on the thermodynamic equilibrium assumption, where the local masses of the constituents are partitioned into either the vapor or liquid phases subject to the local equilibrium constraints at each point in the computational mesh at the end of each time-step. The computational model is validated using available experimental data, with the results demonstrating good agreement. Given the fact that experimental determination of the deposition under human inhalation conditions is extremely difficult, this modeling approach can be considered as a practical method to estimate deposition of aerosol constituents in the upper respiratory tract.

Computational fluid dynamics simulation of full breathing cycle for aerosol deposition in trachea: Effect of breathing frequency

Abstract Aerosols have been widely used in the treatment of certain airway diseases. With different breathing conditions of patients, the flow pattern might not cause the aerosol to transport and deposit on the desired bronchial section. In this study, computational fluid dynamics simulations based on the Euler–Euler method were successfully used to evaluate the airflow behavior when an electrostatic charge was present. The three-dimensional domain was acquired and derived from the computed tomography scan of the patient. Three breathing frequencies were investigated. The instantaneous contour plot revealed that the particles migrated to the wall since charged particles will move from the high to the low potentials. It was found that the variation of the breathing frequency plays a significant role on designated particle deposition region. At a short flow time, the particles only traveled and deposited on the upper part of the airway, whereas as the time flow increased the particles tended to increasingly accumulate on the lower parts of the airway. The electrostatic charge model for aerosol deposition has shown that the further design of aerosol transport must take an average breathing frequency into consideration. The wall shear stress, oscillatory flow velocity index, granular temperature, granular pressure and skin friction coefficient were able to imply the amount of solid particles deposited within the system. All the purposed indices can be used as preliminary indicators for indicating a potential deposition location of the aerosol.

Validation of Modified ART Mod 2 Code through Comparison with Aerosol Deposition of Cesium Compound in Phébus FPT3 Containment Vessel

Evaluation of aerosol deposition in the containment vessel is an important step for the assessment of radioactive material release to the environment. ART Mod 2 is a calculation code that is used for evaluation of aerosol deposition in the containment vessel. The authors modified aerosol deposition models of ART Mod 2, namely, gravitational settling model, Brownian diffusion model, diffusiophoresis model, and thermophoresis model in order to increase potential of capturing the deposition phenomena. This study aims to compare the simulated results of modified ART Mod 2 with aerosol deposition of cesium compounds in the containment vessel of Phébus FPT3 experiment, in order to validate modified ART Mod 2 code. It is found that aerosol deposition using modified ART Mod 2 agrees with Phébus FPT3. Prediction of Brownian diffusion is significantly improved due to the consideration of turbulent damping process. Cesium mass flow rate and aerosol size are factors that can significantly influence the uncertainty of the results. When conditions of single volumes are carefully selected to match those of the Phébus FPT3 experiment, modified ART Mod 2 can predict aerosol deposition in Phébus FPT3 with relative accuracy.

Surface–atmosphere exchange of inorganic water-soluble gases and associated ions in bulk aerosol above agricultural grassland pre- and postfertilisation

Abstract. The increasing use of intensive agricultural practices can lead to damaging consequences for the atmosphere through enhanced emissions of air pollutants. However, there are few direct measurements of the surface–atmosphere exchange of trace gases and water-soluble aerosols over agricultural grassland, particularly of reactive nitrogen compounds. In this study, we present measurements of the concentrations, fluxes and deposition velocities of the trace gases HCl, HONO, HNO3, SO2 and NH3 as well as their associated water-soluble aerosol counterparts Cl−, NO2-, NO3-, SO42- and NH4+ as determined hourly for 1 month in May–June 2016 over agricultural grassland near Edinburgh, UK, pre- and postfertilisation. Measurements were made using the Gradient of Aerosols and Gases Online Registrator (GRAEGOR) wet-chemistry two-point gradient instrument. Emissions of NH3 peaked at 1460 ngm-2s-1 3 h after fertilisation, with an emission of HONO peaking at 4.92 ngm-2s-1 occurring 5 h after fertilisation. Apparent emissions of NO3- aerosol were observed after fertilisation which, coupled with a divergence of HNO3 deposition velocity (Vd) from its theoretical maximum value, suggested the reaction of emitted NH3 with atmospheric HNO3 to form ammonium nitrate aerosol. The use of the conservative exchange fluxes of tot-NH4+ and tot-NO3- indicated net emission of tot-NO3-, implying a ground source of HNO3 after fertilisation. Daytime concentrations of HONO remained above the detection limit (30 ng m−3) throughout the campaign, suggesting a daytime source for HONO at the site. Whilst the mean Vd of NH4+ was 0.93 mm s−1 in the range expected for the accumulation mode, the larger average Vd for Cl− (3.65 mm s−1), NO3- (1.97 mm s−1) and SO42- (1.89 mm s−1) reflected the contribution of a super-micron fraction and decreased with increasing PM2.5∕PM10 ratio (a proxy measurement for aerosol size), providing evidence – although limited by the use of a proxy for aerosol size – of a size dependence of aerosol deposition velocity for aerosol chemical compounds, which has been suggested from process-orientated models of aerosol deposition.