Wall shear stress gradient analysis within an idealized stenosis using non-Newtonian flow

Area of Science:

• Cardiovascular hemodynamics
• Biomedical engineering
• Fluid dynamics

Background:

• Endothelial function is regulated by wall shear stress (WSS) magnitude and gradients.
• Flow separation and reversal are known in high-grade stenoses, but WSS patterns in moderate stenoses are poorly understood.

Purpose of the Study:

• To investigate the wall shear stress (WSS) patterns within mild to moderate carotid artery stenoses.
• To characterize the spatiotemporal dynamics of WSS and WSS gradients in stenotic lesions.

Main Methods:

• Computational fluid dynamics (CFD) analysis using a non-Newtonian blood model.
• Axisymmetric geometry simulating 25%, 50%, and 75% stenoses.
• High-resolution mesh with boundary-layer enrichment for accurate near-wall WSS gradient (WSSG) computation.

Main Results:

• Secondary flow patterns and near-wall flow reversal were observed within stenoses.
• A focal region of retrograde WSS migrated cyclically during the cardiac pulse.
• Zones of zero WSS and high WSSG were identified within the stenosis, shifting with severity and time.

Conclusions:

• Luminal WSS exhibits dynamic direction reversal and high spatial gradients even in moderate stenoses.
• These hemodynamic alterations create a microenvironment promoting endothelial dysfunction and stenosis progression.
• Findings elucidate complex vessel wall hemodynamics in clinical stenoses.