This paper describes the particle trapping mechanism in blood flow in different arterial bifurcation models. Using the software ICEM-CFD, three-dimensional models of arterial bifurcations are established and meshed with structured grids. Compared to unstructured grids, structured grids have advantages of fast generation, high quality, simple data structure and more accurate calculation of viscous regions near the walls. For validation of CFD calculations, a T-junction model with a square cross-section and lateral size of 4mm is analyzed and Navier-Stokes (RANS) equations are solved for single phase laminar flow using the commercial CFD software ANSYS Fluent. The numerical data for pressure gradient and axial velocity along the vortex core is extracted and analyzed in CFD-POST; the computations are in good agreement with the experimental data. After validation, Eulerian simulations are performed by using the Discrete Phase Model (DPM) for two-phase flow with particles in two different bifurcation models. Both models have a circular cross-section and diameter of 20mm.  One of the models is a T-junction while the other model is a Y-junction with two outlet pipes at 90° angle. The inlet velocity profiles are all parabolic with average Reynolds numbers between 200 and 900. By changing the average Reynolds number of the flow and the particle diameters, the mechanism of particle trapping was first investigated in laminar flow. The results showed that in case of T-junction flow when 200 \< Re \< 900, larger low-density particles are more easily trapped in the vortex core while smaller particles are unable to reach the axis of the vortex. It was also found that the particle trapping is only temporary when Re \< 300, while permanent trapping can be observed when Re \> 350 which is caused by the vortex breakdown phenomenon. The contours of velocity magnitude, pressure and wall shear stress are also obtained and analyzed. The effect of Non-Newtonian flow assumption is also investigated by using the Power law and Carreau models; no significant difference was found for both the flow field and particle trapping. Finally, turbulent flow computations at Re = 3,000 were performed  using the  SST k-ω and Wray-Agarwal turbulence models; computations showed that although the flow field was turbulent, the vortex breakdown and particle trapping exhibited similar behavior as in case of high Reynolds number laminar flow. These results have implications in understanding the hemodynamic flows in arterial bifurcations without and with stenosis.  


Blood Flow Simulations of Particle Trapping in Models of Arterial Bifurcations

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.