  Numerous studies suggest that disturbed shear, causing endothelium
dysfunction, can be related to neighboring vortex structures. With this
motivation, this study presents a methodology to characterize the vortex
structures. Precisely, we use mapping and characterization of vortex
structures' changes to relate it with the hemodynamic indicators of disturbed
shear. Topological features of vortex core lines (VCLs) are used to quantify
the changes in vortex structures. We use the Sujudi-Haimes algorithm to extract
the VCLs from the flow simulation results. The idea of relating vortex
structures with disturbed shear is demonstrated for cerebral arteries with
aneurysms virtually treated by inserting foam in the sac. To get
physiologically realistic flow fields, we simulate blood flow in two
patient-specific geometries before and after foam insertion, with realistic
velocity waveform imposed at the inlet, using the Carreau-Yashuda model to
mimic the shear-thinning behavior. With homogenous porous medium assumption,
flow through the foam is modeled using the Forcheimmer-Brinkmann extended Darcy
model. Results show that foam insertion increases the number of VCLs in the
parent lumen. The average length of VCL increases by 168.9% and 55.6% in both
geometries. For both geometries under consideration, results demonstrate that
the region with increased disturbed shear lies in the same arterial segment
exhibiting an increase in the number of oblique VCLs. Based on the findings, we
conjecture that an increase in oblique VCLs is related to increased disturbed
shear at the neighboring portion of the arterial wall.
