Pulsatile non-Newtonian blood flow in arterial aneurysms: Parametric hemodynamic characterization using the finite volume incompressible lattice Boltzmann method

Arterial aneurysms pose a significant public health challenge, with their rupture leading to life-threatening cardiovascular complications. The present study investigates the interplay between aneurysm size, pulsatile flow conditions (Reynolds and Womersley numbers), blood rheology (Carreau number), and key hemodynamic indices—time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and reverse flow fraction (RFF)—to characterize the hemodynamic environment associated with aneurysm progression and rupture risk. Pulsatile non-Newtonian blood flow is simulated using the finite volume incompressible lattice Boltzmann method (FV-iLBM), which captures shear-rate-dependent viscosity through the Carreau model while recovering the incompressible Navier–Stokes equations on unstructured meshes without an iterative pressure–velocity coupling. Increasing Reynolds number raises peak TAWSS and intraluminal pressure while reducing the wall area with OSI >0.20 from 64% to 2.65% (Re=50–200)—exposing competing inertial and oscillatory pathways whose dominance shifts with Re. Higher Womersley numbers amplify shear-layer oscillations and separation dynamics, whereas lower Carreau numbers sustain an elevated effective viscosity that suppresses vortical structures and lowers OSI. Aneurysm size critically modulates these effects: larger aneurysms generate a peak RFF roughly twice that of smaller lesions (∼16% vs ∼7.5%), a distal peak TAWSS about 16% higher, and an 18% collapse of centerline velocity, whereas smaller aneurysms exhibit higher local OSI peaks. By resolving these competing mechanisms, the study demonstrates that no single index captures aneurysm rupture risk and that geometric growth simultaneously escalates peak mechanical stress, expands the atheroprone wall footprint, and elevates the wall pressure loading.