Instability modes and transition of pulsatile stenotic flow: pulse-period dependence
Instability modes and transition of pulsatile stenotic flow: pulse-period dependence
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脉动狭窄血流的不稳定模式和转变：脉冲周期依赖性
DOI：
10.1017/s0022112006003740
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发表时间：
2007
影响因子：
3.7
通讯作者：
S. Sherwin
中科院分区：
文献类型：
--
作者：
H. Blackburn;S. Sherwin
采用全局Floquet稳定性分析和直接数值模拟方法，研究了具有光滑轴对称收缩的圆管内简单非可逆脉动流动的失稳模式。分段平均脉动流用一个谐波分量叠加在时间平均流上表示。我们之前已经确定了一种周期加倍的全球不稳定机制，这种机制与每次脉冲从狭窄喉部喷射出的涡旋环的交替倾斜有关。在这里，我们表明，虽然涡旋环的交替倾斜是与长脉冲周期（或低沃默斯利数）相关的相对较大的减速速度的主要不稳定模式，但对于与较短脉冲周期相关的较低减速速度，主要不稳定通常表现为在每个涡旋环上生长的低波数的方位波（威德纳尔不稳定模式）。所考虑的流动类型也支持对流剪切层的不稳定性。为了深入了解这些具有更短时间周期的不稳定类型的比较作用，我们还对上述全球不稳定的基流引入了高频低振幅扰动。对于所考虑的参数范围，我们观察到主要的Floquet不稳定性的主要特征仍然存在，但是对流不稳定性的额外存在可能具有不稳定效应，特别是对于长脉冲周期。
The instability modes arising within simple non-reversing pulsatile flows in a circular tube with a smooth axisymmetric constriction are examined using global Floquet stability analysis and direct numerical simulation. The sectionally averaged pulsatile flow is represented with one harmonic component superimposed on a time-mean flow. We have previously identified a period-doubling global instability mechanism associated with alternating tilting of the vortex rings that are ejected out of the stenosis throat with each pulse. Here we show that while alternating tilting of vortex rings is the primary instability mode for comparatively larger reduced velocities associated with long pulse periods (or low Womersley numbers), for lower reduced velocities that are associated with shorter pulse periods the primary instability typically manifests as azimuthal waves (Widnall instability modes) of low wavenumber that grow on each vortex ring. Convective shear-layer instabilities are also supported by the types of flow considered. To provide an insight into the comparative role of these types of instability, which have still shorter temporal periods, we also introduce high-frequency low-amplitude perturbations to the base flows of the above global instabilities. For the range of parameters considered, we observe that the dominant features of the primary Floquet instability persist, but that the additional presence of the convective instability can have a destabilizing effect, especially for long pulse periods.
DOI：
10.1115/1.1427042
发表时间：
2002-02-01
影响因子：
1.7
作者：
Stroud, JS;Berger, SA;Saloner, D
通讯作者：
Saloner, D