Initial instabilities of a granular bed sheared by a turbulent liquid flow: length-scale determination
Initial instabilities of a granular bed sheared by a turbulent liquid flow: length-scale determination
复制标题
湍流液体流剪切的颗粒床的初始不稳定性：长度尺度测定
DOI：
10.1590/s1678-58782010000400008
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发表时间：
2010
影响因子：
2.2
通讯作者：
E. Franklin
中科院分区：
文献类型：
--
作者：
E. Franklin
在自然界和工业中经常发现颗粒物质通过流体流动的输送。当水流作用在颗粒床上的剪应力达到一定限度时，就会形成一个移动的颗粒层，称为推移质，其中颗粒与颗粒床的固定部分保持接触。在这些条件下，一个最初平坦的颗粒床可能是不稳定的，产生波纹和沙丘，如在沙漠中观察到的，但也在管道输送沙子。有证据表明，这些形式具有与其初始波长相关的非典型长度。因此，初始线性不稳定性的长度尺度是理解观测到的典型结构的关键。本文从理论上研究了无自由面效应的紊流剪切颗粒床在推移质作用下的初始不稳定性。这项研究包括一个线性稳定性分析，考虑到流体流动，松弛和重力的影响，它是比较发表的实验数据。与以往的研究不同，本文提出当流体为液体时，床形的初始波长随流动条件而变化。
The transport of granular matter by a fluid flow is frequently found in nature and in industry. When the shear stresses exerted by the fluid flow on a granular bed are bounded to some limits, a mobile granular layer known as bed-load takes place, in which the grainsstay in contact with the fixed part of the granular bed. Under these conditions, an initiallyflat granular bed may be unstable, generating ripples and dunes, such as those observed indeserts, but also in pipelines conveying sand. There are evidences that these forms have atypical length correlated to their initial wavelength. So, the length-scale of the initial linear instabilities is a key point to understand the typical structures observed. This paper presents a theoretical study of the initial instabilities on a granular bed sheared by aturbulent liquid flow without free-surface effects, when bed-load is present. This studyconsists of a linear stability analysis, taking into consideration fluid flow, relaxation and gravity effects, and it is compared to published experimental data. It is proposed here,differently from many previous studies, that the initial wavelength of bed-forms varies with flow conditions when the fluid is a liquid.