Naseri, A.Sipkens, T. A.Rogak, S. N.Olfert, J. S....
15页
查看更多>>摘要：Tandem centrifugal particle mass analyzer (CPMA)-single-particle soot photometer (SP2) arrangements provide a measure of the non-refractory components of soot. In such a system, the CPMA is used to classify particles by mass-to-charge ratio (i.e., total particle mass m(p)), and the SP2 measures the mass of rBC (i.e., m(rBC)) within each particle. Data inversion can then be used to compute the two-dimensional total particle-non-refractory black carbon (rBC) (m(p)-m(rBC)) distribution, mapping out the distribution of non-refractory material on rBC particles. He present study derives the optimum sampling settings (i.e., the number of CPMA setpoints per decade, the number of SP2 bins per decade, CPMA resolution, and the number of SP2 counts per CPMA setpoint) to accurately reconstruct m(p)-m(rBC) distributions. Monte Carlo sampling is used to realize the sensitivity of reconstruction error to experimental inputs across a range of distribution widths. General recommendations for a typical aged atmospheric aerosol include: (i) large numbers of SP2 bins per decade (n(s)' = 64), (ii) a preference for higher SP2 sampling counts per CPMA set point (N-s > 10(4)), (iii) a moderate number of CPMA setpoints per decade (n(c)' = 3 to 8), (iv) CPMA resolution around 1.0, and (v) a high CPMA flow rate (1.5 L/min). These settings generally result in reconstruction accuracies below 3%. These recommendations vary based on the concentration of the aerosol, the time available for the measurement, and the width of the distribution. Optimized CPMA-SP2 settings are presented for example distributions as a function of aerosol concentration and desired measurement time.
查看更多>>摘要：Predicting the fate of nasally administered drugs is important for the understanding and possible improvement of in vivo performance. When computational fluid-particle dynamics (CFPD) results are coupled with a physiologically based pharmacokinetic (PBPK) model, drug concentrations in the blood stream can be obtained. Specifically, hybrid CFPD-PBPK simulations can predict inhaled particle transport, deposition, and uptake in the nasal mucus layers and subsequently absorbed drug migration from the nasal cavity to the blood stream.The computer simulation results of Chari et al. (2021) were used as input to a basic PBPK model to track the deposited and dissolved drugs from the nasal cavities to the blood stream. Employing the open-source toolbox OpenFOAM, our PBPK model predictions were compared with experimental in vivo data sets for different corticosteroids. The relative differences between experimental and simulated values of PK metrics, following administration of mometasone furoate nasal spray, were all 7% or less. Drug plasma concentrations based on different drug parameters, such as solubility and partition coefficient, were studied as well. The drug concentration in the plasma was found to increase with an increase in drug solubility (Cs = 0.02 mg/ml, 0.1 mg/ml, 0.2 mg/ml). The same trend was observed for different partition coefficients (Kow = 5e-3, 2, 5000), where the plasma concentration curve peaked for a partition coefficient of 5000. It was also observed that drug dosage controls the amount of residual drug concentrations in the plasma with the passage of time. Two different drug dosages were studied, ie, 50 mu g and 800 mu g, with the former being completely absorbed in the plasma after 8 h; however, in the latter case the drug was not completely absorbed after that time interval. These modeling and simulation results are useful for planning aspects in drug development, as the predictions provide physical insight to differences in device, formulation, and dosage selection.
Feng, YuPatil, AbhijeetKulkarni, NandanSingh, Gur Jai Pal...
26页
查看更多>>摘要：Documentation of comparability between generic inhaler designs and the reference listed drug (RLD) inhalers is essential for regulatory approval of the products. Such assessments need high-fidelity numerical methods to accurately predict the transport, interactions, and deposition of orally inhaled drug products (OIDPs) in the human respiratory systems delivered via inhalers such as dry powder inhalers (DPIs). To explicitly model the particle-particle and particle-wall interactions for OIDPs, this study developed a computational fluid dynamics (CFD) and discrete element method (DEM) to examine drug delivery efficiency, determine emitted aerodynamic particle size distributions (APSDs), and quantify the resultant lung depositions of both lactose carriers and active pharmaceutical ingredient (API) particles. Numerical parametric studies were also performed with multiple actuation flow rates, carrier shapes, and DPI designs. Spiriva (TM) Handihaler (TM) (SH) and a generic DPI were selected in this study. The comparability assessment between the generic DPI and SH has been numerically performed. Specifically, CFD-DEM simulations were run at actuation flow rates of 30, 39, 60, and 90 L/min. Simulations were performed for both spherical and elongated lactose carrier particles with aspect ratios of 1, 5, and 10. Using the emitted APSDs as the mouth inlet conditions, the transport and deposition of API and lactose carriers from mouth to the tracheobronchial tree were also simulated. Numerical results indicate that with the same particle volume, the shape of lactose carriers can significantly influence the DPI delivery efficiency without a monotonic trend, due to the complex resuspension effect after deposition. However, the shape effect of lactose carriers is not significant on the lung deposition patterns of the API. Low actuation flow rates could potentially enhance the overall DPI-airway drug delivery efficiency. Using spherical lactose carriers, the comparability between the generic DPI and SH is demonstrated at all four actuation flow rates. The CFD-DEM model provides a feasible pathway on how to use CFD and DEM to evaluate the comparability between inhalers. The modeling framework also can help obtain new insights on transport dynamics of actines in DPIs to lung, thereby reducing the cost of generic product innovations and accelerating product review and approval.
查看更多>>摘要：Monodisperse packed beds have long been used as surrogate models to predict the filtration performance of particulate filters using analytical methods. In recent years, however, polydisperse packed beds have received special attention as they have the potential to better represent the microstructure of porous filter walls. In this paper, an analytical model for the filtration performance of clean polydisperse packed beds is derived based on the well-proven classical packed bed filtration theory. Predictions of the newly developed model were compared to the results of numerical simulations of the filtration performance of two polydisperse packed beds. The proposed filtration model was in considerably better agreement with the simulations than previous analytical models.
Salminen, TeemuLehtinen, Kari E. J.Kaipio, Jari P.Russell, Vincent...
16页
查看更多>>摘要：This paper focuses on the numerical approximation of the general dynamic equation of aerosols (GDE), an integro-partial differential equation, which models the temporal evolution of aerosol number distributions. More specifically, we study the applicability of the finite element method (FEM) to numerically approximate the GDE at different conditions. In addition to applying the conventional Galerkin FEM to the GDE, we also introduce its extension, the Petrov-Galerkin FEM to improve the stability of the approximation. The FEM approximations are compared against the so-called sectional method, based on the finite difference approximation, which is commonly used for the numerical approximation of the GDE. The FEM schemes and the sectional method are validated with series of numerical simulations, where an accurate solution of GDE is available. In these simulations, we consider special cases of pure condensation and coagulation, as well as cases including both of these processes. The accurate solutions - to which numerical approximations are compared - consist of either the analytical solutions or an accurate solution to the discrete GDE, where the particle size range is discretized into intervals of the size of a monomer, and the condensation process is modeled as an interaction between aerosol particles and monomers. The results of this paper demonstrate that while in the solution of the coagulation problem, the conventional sectional method is more efficient than the FEM, in cases of the condensation equation and the condensation-dominated GDE, the FE approximations outperform the sectional method - yielding a desired level of accuracy of the solution using less discretization points and in computation time which can be even orders of magnitude lower than with the sectional method.
查看更多>>摘要：We evaluate the outward and inward protection efficiencies of different mask types (N95, surgical and two cloth mask designs) taking into account the imperfect fit on the wearer. To this end, we built a manikin to simulate exhaling, coughing and inhaling of aerosol droplets 0.3-5.0 mu m in diameters. The protection efficiencies depend on many factors, including the droplet size, the mask fit and the presence of a filter layer. Here, we show that cloth and surgical masks with a non-woven filter layer can achieve a combined outward and inward protection efficiencies between 50% and 90%. Removing the filter layer greatly reduces the protection efficiency to below 20% for the smallest droplet size. While a well-fitted N95 masks offer protection efficiency close to 100%, a poorly fitted N95 mask with gaps offers less protection than a well-fitted surgical/cloth mask with filter layer. We also found that double masking-the wearing of cloth mask on top of a surgical mask-offers little to no additional protection as compared to a single cloth/surgical mask. The results of our work can inform the implementation of mask mandates to minimize airborne transmissions of coronavirus disease of 2019 (COVID-19).
查看更多>>摘要：This paper focuses on simultaneous, time-and space-resolved measurements of particle size distributions in three different closed indoor environments (small office room, elementary-school classroom, and seminar room) applying mobile air filters in four scenarios (decay curves, filtra-tion while people are present, a temporal strong point source, impact of filter orientation & cross-flow ventilation). The experiments reveal, that mobile indoor air filters, equipped with high-performance filter media (HEPA -quality), remove particles in the investigated rooms in rele-vant submicron size classes (x < 1 mu m) efficiently and uniformly over time. For the description of the local decrease in particle concentration a simple mathematical model based on a transient continuous stirred tank reactor was applied. The local decay curves obtained in the different room-types were compared to simulated ones assuming ideal mixing of the indoor air. The real-room scenarios show a slower particle decay than the predicted ones assuming ideal mixing of the indoor air. The experiments reported in this contribution demonstrate, that indoor air filters, operated with a filtration rate of 3.5 h(-1) and positioned correctly, are capable of lowering the particle concentration in all relevant size classes in real-world closed indoor envi-ronments slowly over time (e.g. a reduction in particle concentration of 50 % after 30 min in a classroom w/o particle sources). In the investigated set-ups, at filtration rates above 9 h(-1), the filters' performance is close to cross-flow window-ventilation. The experiments reveal, that mo-bile air filters cannot avoid close distance transmission of submicron aerosol particles from one person to another. Therefore, they do not replace any of the well-known methods to avoid aerosol-driven infection (like wearing an efficient face mask correctly, limiting the number of people and time of stay in closed indoor environments, frequent ventilation). Mobile air filter devices may represent an additional component in an entire prevention strategy, especially when rooms cannot be ventilated regularly, efficiently or the constellation of people in groups changes frequently (e.g. waiting areas).
查看更多>>摘要：Understanding the transport and deposition of fibers in the respiratory airway is of great significance for the exposure assessment to non-spherical contaminants. Due to its complexity, few computational studies physically resolved the fibers' coupled translational and rotational motion in investigating fiber transport behaviors in the 3D human nasal airways. Additional studies are needed to fully understand the role of the fiber lengths in nasal deposition and the practical benchmarking of fiber characterization to its spherical equivalency. This study investigated the transport and deposition of fibrous particles in the human nasal cavity, resolving the coupled translational and rotational motion to fill the gap. For the first time, a detailed single fiber trajectory in the 3D nasal chamber, accounting for the coupled translational and rotational movement, was visually presented. The subtle effects of fiber deposition due to fiber lengths, rotation, and interaction with the local flow stream, were revealed and analyzed. Furthermore, the study identified the relationship between microfiber deposition and fiber lengths in the human nasal cavity. In particular, nasal deposition of the fibrous and spherical particles with the same impaction parameter or aerodynamic diameter was compared and discussed. The study led to the findings that fiber lengths play different roles in affecting the transport and deposition of microfibers in the human nasal cavity. The relative deposition level between elongated fibers and the spherical particles varies depending on the impaction parameter or the aerodynamic diameter. Current findings are well supported by the literature data.
查看更多>>摘要：We present a new approach for micro- and nanoparticle production by in-situ charge reduction of electrospray droplets, which prevents their Coulombic instabilities and allow the efficient transport (extraction) of the particles. A unipolar ion source based on corona discharge generates a controllable ion flux of opposite polarity to the electrospray. The ions are introduced axially into the spray, while the Taylor cone is screened from the ions by an extractor ring electrode. Efficient and steady droplet discharge and extraction through an orthogonal aerosol-extraction tube was attained when the inlet of the tube was near the spray emission and the ring electrode, resulting in dramatic changes in droplets' trajectories. The best extraction conditions (highest filter collections) were associated with the best discharging (lowest residual electrical charge) and the most globular particles. The size distributions on the particles collected on the filters were monomodal and homogeneous, with small relative standard deviations (as small as 10.6%). The use of corona ions significantly expands the range of polymer concentrations over which globular particles with monomodal size distribution can be made by electrospray.
Ratnam, Jayesh JeeveshCheng, WeihaoKurtyigit, Ismail E.DeMauro, Edward P....
14页
查看更多>>摘要：We investigate the effect that an upstream cylinder has on the effective inertial collision efficiency of a downstream cylinder. We consider an initially uniform distribution of particles moving past a cylindrical fiber in a potential crossflow and numerically calculate the resulting particle distribution far downstream of the fiber using finite differences. We then investigate the effect that the downstream distribution of particles has on the effective inertial collision efficiency of a downstream test cylinder oriented parallel to the first. We show that the effective collision efficiency of the test cylinder depends on its relative offset in the transverse direction (normal to the flow) with respect to the upstream cylinder. For relatively small offsets there is complete shielding, and no particles collide with the test cylinder. As the offset increases, a growing effective collision efficiency is observed leading to a significant enhancement relative to the collision efficiency of an isolated cylinder for intermediate offsets and Stokes numbers close to unity. Importantly, we observe relative gains in effective collision efficiency above 100% for a range of Stokes numbers and offset values. For larger offsets and Stokes numbers, the effect of the upstream cylinder on the effective collision efficiency of the test cylinder decreases and eventually becomes negligible. Detailed results are provided for Stokes drag acting on the particles and we also show that a nonlinear drag has a negligible effect on the observed trends for the conditions relevant to air filtration systems. These results suggest that the arrangement of fibers has a substantial effect on inertial particle impaction even when neighboring fibers do not alter the flow field around each individual collector. Moreover, periodic arrangements with specific orientations with respect of the flow could lead to a significant enhancement of the inertial collision of particles on an array of collectors, thus contributing towards a better filtration performance.
NSTL
Elsevier