Velocity and orientation distributions of fibrous particles in the near-field of a turbulent jet

Qi, Guoqiang; Nathan, Graham J.; Lau, Timothy C. W.

doi:10.1016/j.powtec.2015.02.003

Cited by 10 publications

(6 citation statements)

References 21 publications

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“…It has been report 15 that the transport properties of these ellipsoidal particles remain close to those of spherical particles. However, certain interesting concentration and orientation trends were observed which were in agreement with experimental observations [19][20][21][22][23][24] . Similar to spheres, therefore, prolate spheroids were found to accumulate in the viscous sub-layer and preferentially concentrate in regions of low-speed streaks, with a strong dependence on their inertia ) (  p and a minor dependence on their aspect ratio.…”

Section: Introductionsupporting

confidence: 89%

Simulation of inertial fibre orientation in turbulent flow

Njobuenwu

Fairweather

2016

Physics of Fluids

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The spatial and orientational behaviour of fibres within a suspension influences the rheological and mechanical properties of that suspension. An Eulerian-Lagrangian framework to simulate the behaviour of fibres in turbulent flows is presented. The framework is intended for use in simulations of nonspherical particles with high Reynolds numbers, beyond the Stokesian regime, and is a computationally efficient alternative to existing Stokesian models for fibre suspensions in turbulent flow. It is based on modifying available empirical drag correlations for the translation of non-spherical particles to be orientation dependent, accounting for the departure in shape from a sphere. The orientational dynamics of a particle is based on the framework of quaternions, while its rotational dynamics is obtained from translational dynamics, in terms of preferential concentration, is strongly dependent on their inertia and less so on their aspect ratio. However, the contrary is the case for the fibre alignment distribution as this is strongly dependent on the fibre aspect ratio and velocity gradient, and only moderately dependent on particle inertia. The fibre alignment with the flow direction is found to be mostly anisotropic where the velocity gradient is large (i.e. viscous sub-layer and buffer regions), but is virtually non-existent and isotropic where the turbulence is near-isotropic (i.e. channel centre). The present investigation highlights that the level of fibre alignment with the flow direction reduces as a fibre's inertia decreases, and as the shape of the fibre approaches that of a sphere. Short fibres, and especially near-spherical 001 . 1  particles, are found to exhibit isotropic orientation with respect to all directions, whilst sufficiently long fibres align themselves parallel to the flow direction, and orthogonal to the other two co-ordinate directions, and the vorticity and flow velocity gradient directions.2

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Section: Introductionsupporting

confidence: 89%

Simulation of inertial fibre orientation in turbulent flow

Njobuenwu

Fairweather

2016

Physics of Fluids

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“…We first note that fibers with AR = 5 (middle row) and 30 (bottom row) tend to align with the flow streamlines and rotate around the z -axis, either during flow reversals or when subjected to high shear rates close to the wall. Such general trends agree with Qi et al (2015), where the absolute mean angular velocity of fibers increases significantly as they get closer to the region of highest shear, i.e. far from the main axis of the tube.…”

Section: Resultssupporting

confidence: 86%

“…These include for example soot, asbestos fibers, glass wool and carbon nanotubes. The dynamics of inhaled fibers under various respiratory flows have been vastly investigated (Chen et al, 2016; Chen and Yu, 1991; Högberg et al, 2010; Qi et al, 2015; Tian et al, 2012) both through numerical (Marchioli et al, 2010; Tornberg and Shelley, 2004) and experimental (Qi et al, 2013; Shapiro and Goldenberg, 1993) studies. It was found that fibers tend to align with flow streamlines and when inhaled into the pulmonary system, these remain longer airborne as they somewhat act more closely as passive tracers of the flow (T.…”

Section: Introductionmentioning

confidence: 99%

Transport of ellipsoid fibers in oscillatory shear flows: Implications for aerosol deposition in deep airways

Shachar-Berman

Ostrovski

Rosis

et al. 2018

European Journal of Pharmaceutical Sciences

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It is widely acknowledged that inhaled fibers, e.g. air pollutants and anthropogenic particulate matter, hold the ability to deposit deep into the lungs reaching the distal pulmonary acinar airways as a result of their aerodynamic properties; these particles tend to align with the flow and thus stay longer airborne relative to their spherical counterpart, due to higher drag forces that resist sedimentation. Together with a high surface-to-volume ratio, such characteristics may render non-spherical particles, and fibers in particular, potentially attractive airborne carriers for drug delivery. Until present, however, our understanding of the dynamics of inhaled aerosols in the distal regions of the lungs has been mostly limited to spherical particles. In an effort to unravel the fate of non-spherical aerosols in the pulmonary depths, we explore through numerical simulations the kinematics of ellipsoid-shaped fibers in a toy model of a straight pipe as a first step towards understanding particle dynamics in more intricate acinar geometries. Transient translational and rotational motions of micron-sized ellipsoid particles are simulated as a function of aspect ratio (AR) for laminar oscillatory shear flows mimicking various inhalation maneuvers under the influence of aerodynamic (i.e. drag and lift) and gravitational forces. We quantify transport and deposition metrics for such fibers, including residence time and penetration depth, compared with spherical particles of equivalent mass. Our findings underscore how deposition depth is largely independent of AR under oscillatory conditions, in contrast with previous works where AR was found to influence deposition depth under steady inspiratory flow. Overall, our efforts underline the importance of modeling oscillatory breathing when predicting fiber deposition in the distal lungs, as they are inhaled and exhaled during a full inspiratory cycle. Such physical insight helps further explore the potential of fiber particles as attractive carriers for deep airway targeting.

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“…The pneumatic transport of fibres in an axial airflow was modelled numerically by Lin et al [9] and experimentally by Capone et al [10] and Qi et al [11]. In these studies, fibres were modelled as rigid bodies with relatively low aspect ratio (i.e.…”

Section: Introductionmentioning

confidence: 99%