Purpose

Screening 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).

Method

We 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.

Results

Only 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.

Conclusions

The 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.

中文翻译：

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狭窄后患者特定颈动脉狭窄流体动力学中的高频波动：计算流体动力学策略研究。

目的

无症状的颈动脉狭窄的筛查是通过听诊颈动脉挫伤进行的，但敏感性较差。取而代之的是，有人建议将颈动脉擦伤检测为脖子的皮肤振动。我们在这里迈出了计算流体动力学概念验证研究的第一步，并研究了我们的数值方法在捕获狭窄后流量中频繁波动时的鲁棒性。目的是从务实的角度找到一种理想的解决方案，将欠解决的直接数值模拟（DNS）方法与三种常见的大型涡流模拟（LES）模型（静态/动态Smagorinsky和西格玛（Sigma）。

方法

我们通过对恒定流量的狭窄颈动脉分叉进行时空精细化研究，找到了一种参考解决方案。参考解\（\ left（{\ Delta x = 1.92 \ times 10 ^ {-4} \; {\ text {m}}，\; \\ Delta t = 5 \ times 10 ^ {-5} \; {将\ text {s}}} \ right）\）与LES进行比较，以获得恒定流量和脉动流量。

结果

只有Sigma和Dynamic Smagorinsky模型能够复制参考溶液的流场以进行脉动仿真，但是Sigma模型的计算成本较低。但是，没有一个子网格规模模型能够在峰值收缩期恒定流量模拟中复制高频流量，该模拟具有较高的平均雷诺数。

结论

Sigma模型是模拟脉动后狭窄流场的准确性和成本之间的最佳组合，而对于恒定流量，欠解析DNS方法更好。这些结果可作为将来研究高频流量特征的参考。