Abstract
PurposeScreening of asymptomatic carotid stenoses is performed by auscultation of the carotid bruit, but the sensitivity is poor. Instead, it has been suggested to detect carotid bruit as neck’s skin vibrations. We here take a first step towards a computational fluid dynamics proof-of-concept study, and investigate the robustness of our numerical approach for capturing high-frequent fluctuations in the post-stenotic flow. The aim was to find an ideal solution strategy from a pragmatic point of view, balancing accuracy with computational cost comparing an under-resolved direct numerical simulation (DNS) approach vs. three common large eddy simulation (LES) models (static/dynamic Smagorinsky and Sigma).MethodWe found a reference solution by performing a spatial and temporal refinement study of a stenosed carotid bifurcation with constant flow rate. The reference solution left( {Delta x = 1.92 times 10^{ - 4} ;{text{m}},; Delta t = 5 times 10^{ - 5} ;{text{s}}} right) was compared against LES for both a constant and pulsatile flow.ResultsOnly the Sigma and Dynamic Smagorinsky models were able to replicate the flow field of the reference solution for a pulsatile simulation, however the computational cost of the Sigma model was lower. However, none of the sub-grid scale models were able to replicate the high-frequent flow in the peak-systolic constant flow rate simulations, which had a higher mean Reynolds number.ConclusionsThe Sigma model was the best combination between accuracy and cost for simulating the pulsatile post-stenotic flow field, whereas for the constant flow rate, the under-resolved DNS approach was better. These results can be used as a reference for future studies investigating high-frequent flow features.
Highlights
Carotid stenosis is a progressive and local buildup of plaque in the carotid bifurcation, leading to a local narrowing of the lumen
The Sigma model was the best combination between accuracy and cost for simulating the pulsatile poststenotic flow field, whereas for the constant flow rate, the under-resolved DNS approach was better
The sub-grid scales (SGS) models are applicable for investigating the turbulent-like flow in multiple patients or configurations, and with fluid structure interaction (FSI), how the flow fluctuations can present as skin vibrations on the neck of affected patients
Summary
Carotid stenosis is a progressive and local buildup of plaque in the carotid bifurcation, leading to a local narrowing of the lumen. The major risk consists of plaque rupture with subsequent debris and thrombi being transported downstream where they can cause a blockage leading to a stroke and consequent neurologic deficits.[35]. Asymptomatic carotid artery stenoses (ACAS), which affects 1.6% of the population,[8] are rarely detected unless diagnosed with another associated cardiovascular disease.[42]. A characteristic feature of stenoses is that the downstream flow is turbulent-like, with high-frequent pressure fluctuations.[3] These fluctuations can traverse the soft neck tissue as mechanical waves, and present as a bruit or skin vibration. The stenosis-induced turbulent-like flow is a strong marker for inferring the presence of a stenosis
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