Transitional flow in aneurysms and the computation of haemodynamic parameters

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Cardiovascular Research

Background:

• Aneurysm development is influenced by hemodynamic forces, with studies often focusing on wall shear stress (WSS).
• Current computational fluid dynamics (CFD) approaches typically analyze flow properties over a single cardiac cycle.

Purpose of the Study:

• To investigate the impact of transitional flow on WSS distribution in aneurysms across multiple cardiac cycles.
• To highlight the necessity of extended simulations for accurate hemodynamic index determination.

Main Methods:

• Computational fluid dynamics (CFD) simulations were employed.
• Two case studies were analyzed: abdominal aortic aneurysm and intracranial aneurysm.
• Flow properties and WSS were examined over multiple cardiac cycles to assess transitional flow effects.

Main Results:

• Transitional flow in aneurysms can lead to significantly different WSS distributions in consecutive cardiac cycles.
• The timescale of flow transients relative to the cardiac cycle duration influences WSS variability.
• Larger geometries exhibit persistent transients that seed different flow patterns in each cycle.

Conclusions:

• Accurate time-averaged hemodynamic indices require simulations of numerous cardiac cycles, not just one.
• Comparing indices from at least two successive cardiac cycles is essential to determine statistical convergence.
• Understanding transitional flow dynamics is critical for accurate aneurysm progression modeling.