Experimental Assessment of Compliance Effects on Transitional Flow in Intracranial Aneurysm Models Using Particle Tracking Velocimetry
C. Peng(1), J.J. Kolliyil(1), E.W. Church(2), M.C. Brindise(1)
1: Department of Mechanical Engineering, Pennsylvania State University, University Park, PA 16802, USA
2: Departments of Neurosurgery, Neurology, and Radiology, Penn State Health, Hershey, PA 17033, USA
DOI:
The progression of intracranial aneurysms (IA) is influenced by hemodynamic factors such as wall shear stress and pressure. The underlying flow regime, i.e., laminar versus transitional or turbulent, can substantially alter these quantities. Although aneurysmal flows have traditionally been assumed to be laminar due to their relatively low Reynolds numbers (typically 100–500), studies have increasingly reported the presence of transitional or disturbed flow behavior. However, the presence of non-laminar flow in IAs is debated as no universal metric currently exists to characterize the extent of transitional flow in the aneurysms. A consequence of this is that factors such as wall compliance, which are believed to affect IA flow and transitional flow characteristics, cannot be presently studied. In this work, we address these gaps by introducing a metric to quantify the extent of non-laminar flow in an IA and using it to investigate the effect of wall compliance on flow transition in IAs. Time-resolved particle tracking velocimetry experiments were performed using manufactured compliant patient-specific aneurysm models. Two levels of compliance and three flow rates were tested for comparison. Our new flow-regime metric—based on a two-line fitting approach applied to the energy spectrum—was employed to identify the degree of transition. We observed that the high-compliance model exhibited more complex rotational flow structures with two distinct rotational directions, whereas the low-compliance model resulted in a centrally symmetric rotational flow structure. Furthermore, all configurations exhibited energy spectral characteristics associated with transitional and turbulence-like behavior. The high-compliance model demonstrated an earlier transition than the less compliant model. Overall, these results suggest that increased wall compliance promotes transition and turbulence-like behavior in IAs in general. The findings highlight the important role of wall deformation in modulating flow instability and indicate that rigid-wall assumptions may underestimate the transitional nature and complexity of aneurysmal hemodynamics.
