Linear stability analysis of turbulent flows over dense filament canopies
Linear stability analysis of turbulent flows over dense filament canopies
复制标题
密集丝冠层上湍流的线性稳定性分析
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
R. García
中科院分区：
文献类型：
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作者：
Akshath Sharma;G. Gómez;R. García
本工作的目的是研究冠层参数的变化对它们触发的Kelvin-Helmholtz型不稳定性的影响。这些不稳定性的外观超过长丝冠层已被广泛研究，但目前的工作旨在探讨是否可以通过改变冠层特性操纵的不稳定性。为此，使用线性稳定性分析进行参数研究。对于分析，冠层建模使用两种方法。第一个模型的树冠作为一个可渗透的基板。第二种方法通过作用在冠层内的阻力来解释冠层，并分别研究了冠层动力学的一些影响，即冠层单元的平均弯曲和冠层的动态聚集。使用多孔介质的类比，它示出了刚性冠层的发病的不稳定性是由几何平均的流向和壁正常的渗透率阻力模型表现出一个额外的功能，即错过了多孔模型的阻力系数的最佳值，在该放大的不稳定性是最大的。研究还发现，冠层波动引起的冠丝簇集效应会显著增加不稳定性的放大，其影响程度大于冠丝平均弯曲效应。
The aim of this work is to study the effect of the variation in canopy parameters on the Kelvin-Helmholtz-like instabilities triggered over them. The appearance of these instabilities over filament canopies has been widely studied, but the present work seeks to explore whether the instability can be manipulated by changing canopy properties. To this effect, a parametric study using linear stability analysis is conducted. For the analyses, the canopy is modelled using two methods. The first models the canopy as a permeable substrate. The second accounts for the canopy through drag forces acting on the flow within it. Some effects of canopy dynamics, namely the average bending of the canopy elements and the dynamic clustering of the canopy are also individually studied. Using the porous medium analogy it is shown for rigid canopies that the onset of the instabilities is governed by the geometric mean of the streamwise and wall-normal permeabilities The drag model exhibits an additional feature missed by the porous model i.e. an optimum value of drag coefficient at which the amplification of the instability is maximum. It is also observed that the clustering of filaments caused by the waving of the canopy can significantly increase the amplification of the instability, and has a greater impact than the mean filament bending.