论文标题
振荡动能管流中的动荡动能传输
Turbulent kinetic energy transport in oscillatory pipe flow
论文作者
论文摘要
在生物医学科学和工程的许多领域都出现了层流以及湍流振荡管流。肺气流和血管血流通常是层流，因为作用在生理系统上的剪切力应该很小。但是，随着向湍流的过渡，摩擦损失和剪切应力差异很大。这在例如人工呼吸或狭窄。另一方面，在活塞发动机和往复热/化学过程设备中，湍流或过渡性振荡流影响混合特性，还会影响质量和热传递。与经过广泛研究的统计稳定壁的剪切流相比，几乎没有工作用于发作，放大和湍流的管道流动中的湍流，这是由不稳定的外力驱动的。实验[1，3，6]表明，向湍流的过渡仅取决于一个参数，即re_Δ\ sim re/wo，临界值约为550，至少对于Womersley数字WO> 7。我们执行直接数值模拟（DNS），以较高的价值和更高的价值来扩展该临界值的振动性流动的振动管流动，以扩展这种临界价值。为了更好地了解腐烂流动过程中涉及的物理机制，我们进一步分析了动荡的动能分布及其预算项。
Laminar as well as turbulent oscillatory pipe flows occur in many fields of biomedical science and engineering. Pulmonary air flow and vascular blood flow are usually laminar, because shear forces acting on the physiological system ought to be small. However, frictional losses and shear stresses vary considerably with transition to turbulence. This plays an important role in cases of e.g. artificial respiration or stenosis. On the other hand, in piston engines and reciprocating thermal/chemical process devices, turbulent or transitional oscillatory flows affect mixing properties, and also mass and heat transfer. In contrast to the extensively investigated statistically steady wall bounded shear flows, rather little work has been devoted to the onset, amplification and decay of turbulence in pipe flows driven by an unsteady external force. Experiments [1, 3, 6] indicate that transition to turbulence depends on only one parameter, i.e. Re_δ \sim Re/Wo with a critical value of about 550, at least for Womersley numbers Wo > 7. We perform direct numerical simulations (DNS) of oscillatory pipe flows at several combinations of Re and Wo to extend the validity of this critical value to higher Wo. To better understand the physical mechanisms involved during decay and amplification of the turbulent flow, we further analyse the turbulent kinetic energy distribution and its budgets terms.
