Modeling Transport and Deposition Efficiency of Oblate and Prolate Nano- and Micro-particles in a Virtual Model of the Human Airway

Holmstedt, Elise; Åkerstedt, Hans O.; Lundström, T. Staffan; Högberg, Sofie

doi:10.1115/1.4032934

Cited by 8 publications

(5 citation statements)

References 27 publications

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“…Solid round particles with a density of 1200 kg/m 3 were utilized with an injection rate of 1.3 g/mm 3 /s for all particles throughout the inhalation process. Other studies have demonstrated the importance of modeling the Brownian motion [37,38] for nanoparticles. However, the present investigation does not include modeling of the Brownian motion due to the dominance of the flow inertial on micron particle depositions in large and medium airways.…”

Section: Computational Models Of Particle Transport Andmentioning

confidence: 99%

Particulate Deposition in a Patient With Tracheal Stenosis

Taherian

Rahai

Bonifacio

et al. 2017

Journal of Engineering and Science in Medical Diagnostics and Therapy

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The presence of obstructions such as tracheal stenosis has important effects on respiratory functions. Tracheal stenosis impacts the therapeutic efficacy of inhaled medications as a result of alterations in particle transport and deposition pattern. This study explores the effects of the presence and absence of stenosis/obstruction in the trachea on air flow characteristics and particle depositions. Computational fluid dynamics (CFD) simulations were performed on three-dimensional (3D) patient-specific models created from computed tomography (CT) images. The analyzed model was generated from a subject with tracheal stenosis and includes the airway tree up to eight generations. CT scans of expiratory and inspiratory phases were used for patient-specific boundary conditions. Pre- and post-intervention CFD simulations' comparison reveals the effect of the stenosis on the characteristics of air flow, transport, and depositions of particles with diameters of 1, 2.5, 4, 6, 8, and 10 μm. Results indicate that the existence of the stenosis inflicts a major pressure force on the flow of inhaled air, leading to an increased deposition of particles both above and below the stenosis. Comparisons of the decrease in pressure in each generation between pre- and post-tracheal stenosis intervention demonstrated a significant reduction in pressure following the stenosis, which was maintained in all downstream generations. Good agreements were found using experimental validation of CFD findings with a model of the control subject up to the third generation, constructed via additive layer manufacturing from CT images.

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Section: Computational Models Of Particle Transport Andmentioning

confidence: 99%

Particulate Deposition in a Patient With Tracheal Stenosis

Taherian

Rahai

Bonifacio

et al. 2017

Journal of Engineering and Science in Medical Diagnostics and Therapy

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“…For example, even small deviations from a perfect axisymmetric rod shape can lead to the appearance of doubly periodic and chaotic orbits, and these have been studied both theoretically and experimentally [8][9][10] . The proximity of channel walls [11][12][13][14][15] , inertia 6 and the viscoelasticity of the shearing fluid 16 have also been shown to perturb the Jeffery solution. Furthermore, noise may also affect the orbits: for smaller rods, where Brownian motion (i.e.…”

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confidence: 99%

Dynamics of individual Brownian rods in a microchannel flow

et al. 2019

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We study the orientational dynamics of heavy silica microrods flowing through a microfluidic channel. Comparing experiments and Brownian dynamics simulations we identify different particle orbits, in particular in-plane tumbling behavior, which cannot be explained by classical Jeffery theory, and we relate this behavior to the rotational diffusion of the rods. By constructing the full, three-dimensional, orientation distribution, we describe the rod trajectories and quantify the persistence of Jeffery orbits using temporal correlation functions of the Jeffery constant. We find that our colloidal rods lose memory of their initial configuration in about a second, corresponding to half a Jeffery period.Understanding the physics of a micron-scale, elongated particle moving in viscous flows is widely relevant. Examples include the effect of shape on nano-particle assisted drug delivery 1 , the dynamics of flowing suspensions of bacteria 2 , nanoengineering optically anisotropic devices 3 and the processing of food and pastes 4 . The orientational behaviour of a single, non-Brownian, ellipsoidal rod in a simple shear flow was analysed theoretically in a classic paper by Jeffery in 1922 5 who found that the orientation of an axisymmetric ellipsoid undergoes a periodic motion on the unit sphere. Assuming that the flow is in the x direction and that the shear gradient is along z [see also Fig. 1(a) for non-uniform shear], the specific orbit a particle follows is determined by its aspect ratio λ , the shear rateγ and the Jeffery constant C = n 2x + n 2 z /λ 2 /n y which depends on the initial orientation of the rod and ranges from -∞ to ∞. Here, the unit vector n = n xx + n yŷ + n zẑ points along the long axis of the particle. For C = ±∞ the rod rotates in the xz-plane. It is oriented along the direction of flow for most of the time, but periodically "tumbles", i.e. flips its orientation by 180 • . For smaller values of C, the motion has a finite y-component, and looks very similar to the trajectory of the paddles of a kayak if viewed from the side, hence the term "kayaking" for these orbits. At C = 0, the rod orients along the y-direction and only rotates around its long axis. This last type of motion is called "log-rolling", and has been shown to be unstable for rod-shaped particles 6 . Experiments on single rods, carried out in the non-Brownian regime, have demonstrated the applicability of Jeffery's ideas 7 .Subsequent research has shown how the many perturbations present in flowing channels can affect the reproducibility and longevity of the orbits. For example, even small deviations from a perfect axisymmetric rod shape can lead to the appearance of doubly periodic and chaotic orbits, and these have been studied both theoretically and experimentally [8][9][10] . The proximity of channel walls 11-15 , inertia 6 and the viscoelasticity of the shearing fluid 16 have also been shown to perturb the Jeffery solution. Furthermore, noise may also affect the orbits: for smaller rods, where Brownian motion (i.e. thermal noise)...

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“…The Stokes diameters for a prolate spheroid are given by and the ones for oblate spheroids are given by Holmstedt et al. 43 …”

Section: Simulation Set-upmentioning

confidence: 99%

Modelling transport and deposition of non-spherical micro- and nano-particles in composites manufacturing

Holmstedt

Åkerstedt

Lundström

2018

Journal of Reinforced Plastics and Composites

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In liquid moulding processes, a fabric is impregnated with a fluid that may contain particles aimed at giving the final product additional and possible smart properties. It is therefore interesting to be able to reveal how the distribution and orientation of such particles are affected by the processing condition. During the manufacturing of the fabric, relatively large channels are formed between bundles of fibres where the impregnating fluid may flow. There are also micro-channels within the bundle that are impregnated by the fluid in the larger channels mainly by capillary action. With focus on fibre bundles along the main flow direction, three main stages of the flow are the flow is leading within the bundles, the flow is moving at equal rate within the bundles and between them and the flow is leading in the channels between the bundles. The latter one of these is in focus in this study, and the capillary action from the larger channels to the micro-channels is modelled as a constant radial velocity. Brownian, gravitational and hydrodynamic forces acting on the particles are studied. The introduction of a radial velocity component drastically increases the deposition rate, and it is clear that while particle shape has a great influence on deposition rates in a flow moving strictly in the direction of the channel, when a radial flow component is introduced the differences seem to disappear.

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Modeling Transport and Deposition Efficiency of Oblate and Prolate Nano- and Micro-particles in a Virtual Model of the Human Airway

Cited by 8 publications

References 27 publications

Particulate Deposition in a Patient With Tracheal Stenosis

Particulate Deposition in a Patient With Tracheal Stenosis

Dynamics of individual Brownian rods in a microchannel flow

Modelling transport and deposition of non-spherical micro- and nano-particles in composites manufacturing

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