Norwegian Defence Research Establishment (FFI), Kjeller, Norway.
Center for Biomedical Computing, Simula Research Laboratory, Fornebu, Norway.
J Biomech. 2014 Mar 21;47(5):1082-90. doi: 10.1016/j.jbiomech.2013.12.023. Epub 2014 Jan 22.
The flow of cerebrospinal fluid (CSF) in a patient-specific model of the subarachnoid space in a Chiari I patient was investigated using numerical simulations. The pulsating CSF flow was modeled using a time-varying velocity pulse based on peak velocity measurements (diastole and systole) derived from a selection of patients with Chiari I malformation. The present study introduces the general definition of the Reynolds number to provide a measure of CSF flow instability to give an estimate of the possibility of turbulence occurring in CSF flow. This was motivated by the fact that the combination of pulsating flow and the geometric complexity of the spinal canal may result in local Reynolds numbers that are significantly higher than the commonly used global measure such that flow instabilities may develop into turbulent flow in these regions. The local Reynolds number was used in combination with derived statistics to characterize the flow. The results revealed the existence of both local unstable regions and local regions with velocity fluctuations similar in magnitude to what is observed in fully turbulent flows. The results also indicated that the fluctuations were not self-sustained turbulence, but rather flow instabilities that may develop into turbulence. The case considered was therefore believed to represent a CSF flow close to transition.
使用数值模拟研究了 Chiari I 患者蛛网膜下腔的特定患者模型中的脑脊液（CSF）流动。使用基于从 Chiari I 畸形患者中选择的测量得出的峰值速度（舒张和收缩）的时变速度脉冲来模拟脉动 CSF 流动。本研究引入了雷诺数的一般定义，以提供 CSF 流动不稳定性的度量，以估计 CSF 流动中可能发生湍流的可能性。这是因为脉动流动和椎管的几何复杂性的组合可能导致局部雷诺数明显高于通常使用的全局度量，从而使这些区域中的流动不稳定性可能发展成湍流。局部雷诺数与推导的统计数据结合使用来描述流动。结果表明，存在局部不稳定区域和局部区域，其速度波动幅度与完全湍流中观察到的速度波动幅度相似。结果还表明，这些波动不是自维持的湍流，而是可能发展成湍流的流动不稳定性。因此，所考虑的情况被认为代表了接近过渡的 CSF 流动。
