Experimental characterization of extreme events of inertial dissipation in a turbulent swirling flow.
Experimental characterization of extreme events of inertial dissipation in a turbulent swirling flow.
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DOI：
10.1038/ncomms12466
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发表时间：
2016-08-31
影响因子：
16.6
通讯作者：
Dubrulle, B.
中科院分区：
文献类型：
--
作者：
Saw, E. -W.;Kuzzay, D.;Faranda, D.;Guittonneau, A.;Daviaud, F.;Wiertel-Gasquet, C.;Padilla, V.;Dubrulle, B.
三维不可压缩Navier-Stokes方程描述了许多流体的运动，是许多物理和工程科学的基石。然而，目前还不清楚它们是否在数学上是适定的，也就是说，它们的解是否随着时间的推移保持正则或发展奇点。即使它表明，奇点，如果存在，只能是罕见的事件，他们可能会引起额外的能量耗散惯性手段。在这里，使用轴对称湍流耗散尺度的测量，我们报告这种惯性能量耗散的估计，并确定当地的极端值事件。我们描述了这些极端事件的拓扑结构，并确定了几种主要类型。它们中的大多数出现在不同速度的区域分离的前锋，而对应于聚焦螺旋，射流和尖点的事件也found. Our结果突出了非平凡的湍流在亚Kolmogorov尺度的可能足迹的奇异性的Navier-Stokes方程。 粘性湍流的经典描述是基于Navier-Stokes方程的公式，该公式假定其解始终保持光滑。Saw等人在耗散尺度上描述了实验湍流中的速度场，并将结果与奇点联系起来。
The three-dimensional incompressible Navier–Stokes equations, which describe the motion of many fluids, are the cornerstones of many physical and engineering sciences. However, it is still unclear whether they are mathematically well posed, that is, whether their solutions remain regular over time or develop singularities. Even though it was shown that singularities, if exist, could only be rare events, they may induce additional energy dissipation by inertial means. Here, using measurements at the dissipative scale of an axisymmetric turbulent flow, we report estimates of such inertial energy dissipation and identify local events of extreme values. We characterize the topology of these extreme events and identify several main types. Most of them appear as fronts separating regions of distinct velocities, whereas events corresponding to focusing spirals, jets and cusps are also found. Our results highlight the non-triviality of turbulent flows at sub-Kolmogorov scales as possible footprints of singularities of the Navier–Stokes equation. The classical description of viscous turbulent flows is based on a formulation of Navier-Stokes equations which assumes its solutions to remain smooth at all times. Saw et al. characterize velocity fields in experimental turbulent flows at dissipative scale, and link the results to the singularities.
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