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Research Papers

Computational Modeling of Thrombotic Microparticle Deposition in Nonparallel Flow Regimes

[+] Author and Article Information
Connie L. Hall

Department of Biomedical Engineering,
The College of New Jersey,
2000 Pennington Road,
Ewing, NJ 08628
e-mail: chall@tcnj.edu

Melissa Calt

Department of Biomedical Engineering,
The College of New Jersey,
2000 Pennington Road,
Ewing, NJ 08628
e-mail: melissaacalt@gmail.com

1Corresponding author.

Manuscript received January 9, 2014; final manuscript received July 26, 2014; accepted manuscript posted August 1, 2014; published online September 4, 2014. Assoc. Editor: Dalin Tang.

J Biomech Eng 136(11), 111002 (Sep 04, 2014) (10 pages) Paper No: BIO-14-1015; doi: 10.1115/1.4028134 History: Received January 09, 2014; Revised July 26, 2014; Accepted August 01, 2014

Thrombotic microparticles (MPs) released from cells and platelets in response to various stimuli are present in elevated numbers in various disease states that increase the risk for thrombotic events. In order to understand how particles of this size may localize in nonparallel flow regimes and increase thrombotic risk, a computational analysis of flow and MP deposition was performed for 3 deg of stenosis at moderate Reynolds number (20 < Re < 80) and for recirculation zones at low Reynolds (∼1) number. The results indicate that MP deposition results primarily from impaction and not by diffusive flux.

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Figures

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Fig. 1

Stenosis geometries (60%, 80%, and 89%) and dimensions. The y dimension is scaled up by a factor of 3 to allow visualization of the full length (scale × 1). The contraction appears sharp as a result of compressing the figure. Refer to Fig. 3 for a magnified view of the contraction zone.

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Fig. 2

The vertical step geometry and dimensions. The y dimension is scaled by a factor of 3 to allow visualization of the full length (scale × 1).

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Fig. 3

Magnified view of computational grids. (a) The computational grid from the prestenotic zone through the contraction zone and into the stenosis and (b) the computational grid in the vicinity of the vertical step.

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Fig. 4

Strain rate as a function of x dimension. The strain rate along the centerline of the bottom wall from a position 0.5 mm before the contraction, through the 0.5 mm contraction and 0.5 mm into the stenotic zone. Each panel displays, for one degree of stenosis the strain rate for Re = 10, 20, 40, and 80. Top panel 60% stenosis, middle panel 80% stenosis, and bottom panel 89% stenosis.

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Fig. 5

Recirculation trace in the expansion zone. Recirculation was evident for Re = 40 (left three panels) and Re = 80 (right three panels) for all degrees of stenosis. The trace indicates a massless fluid particle trajectory indicating a growing recirculation zone with degree of stenosis and Reynolds number. Top two panels 60%, middle panels 80%, and bottom panels 89% stenosis.

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Fig. 6

Recirculation trace in the expansion zone past the vertical step. Recirculation was evident for all Reynolds numbers. The trace indicates a massless fluid particle trajectory indicating a growing recirculation zone with increasing Reynolds number and wall shear rate. From top to bottom, the panels display traces for prestep wall shear rates of 12.5, 50, 400, and 1600 s1.

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Fig. 7

The y velocity component at a position 0.25 μm from the lower wall. The velocity component perpendicular to the bottom wall from the vertical step and downstream 1 mm (1.4 cm ≤ x ≤ 1.5 cm) is displayed for all four flow conditions. The peaks indicate the positions of maximum velocity directed away from (positive values) or toward (negative values) the wall. (a) wall shear rates of 12.5 and 50 s−1 and (b) 400 and 1600 s−1).

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Fig. 8

Correlation of velocity and MP deposition in the contraction zone as a function of Reynolds number and degree of stenosis. Velocity directed toward the bottom wall is displayed as positive and shown in the top panel. The corresponding MP deposition is shown in the bottom panel. Each point represents a parcel of particles and number of particles per parcel increases with increasing Reynolds number. The degree of stenosis, from left to right is 60%, 80%, and 89%. (a) Re = 10; (b) Re = 20; (c) Re = 40; and (d) Re = 80.

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Fig. 9

Parcel trajectories and path of a massless fluid particle from two points at the inlet to the contraction zone. Parcel trajectories are shown as square dots and the fluid trace is a solid line. The panels, from top to bottom, represent 60%, 80%, and 89% stenosis. The traces and trajectories initiate from the same two points at the inlet. The trajectories result in deposition in the contraction zone (the location of the most significant accumulation of deposited parcels) in the 89% stenosis model, but not in the 60% or 80% stenosis.

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Fig. 10

Particle deposition on the bottom wall of the contraction zone. Comparison of the number of particles deposited as a function of Reynolds number and degree of stensosis.

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Fig. 11

Correlation of velocity and MP deposition poststenosis. MPs deposited on the side walls downstream of the stenosis and the expansion zone (2.8 cm < x < 3.15 cm). The degree of stenosis from left to right is 60%, 80%, and 89%. MP deposition across the chamber depth increased correlatively with a peak in the velocity component directed toward the wall.

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