封闭管道中沙纹的形成和迁移：紊流实验
The formation and migration of sand ripples in closed conduits: experiments with turbulent water flows
摘要：
在自然界和工业中经常发现固体颗粒通过流体流动的输送。一些例子是河流和碳氢化合物管道中的沙子运输。当流体流施加在颗粒床上的剪切应力保持适度时，一些颗粒被设置为运动而不使床流化;运动的颗粒形成一个层，称为推移质，该层在移动的同时保持与床的固定部分接触。在推移质条件下，颗粒床可能变得不稳定，产生波纹和沙丘。沙纹通常在封闭的管道和管道中观察到，例如石油管道，下水道系统和疏浚管线。虽然在许多科学领域和工业应用的重要性，波纹的形成在封闭的管道没有得到很好的理解，这个问题仍然是开放的。本文介绍了在紊流闭管水流和推移质条件下沙纹形成和迁移的试验研究。在我们的实验中，充分发展的湍流水流施加在一个透明的通道中的已知粒度的颗粒床，并发生推移质负荷。对于不同的水流量和粒径，生长和迁移的底形被拍摄的高清晰度相机，并开发了一个数字代码，以确定从所获得的图像的波长和celebrations的底形。所得到的结果进行了比较与出版的稳定性分析。
英文摘要：
The transport of solid particles by a fluid flow is frequently found in nature and industry. Some examples are the transport of sand in rivers and hydrocarbon pipelines. When the shear stresses exerted by a fluid flow on a granular bed remain moderate, some grains are set in motion without fluidizing the bed; the moving grains form a layer, known as bed load, that moves while maintaining contact with the fixed part of the bed. Under bed load conditions, the granular bed may become unstable, generating ripples and dunes. Sand ripples are commonly observed in closed conduits and pipes such as in petroleum pipelines, sewer systems, and dredging lines. Although of importance for many scientific domains and industrial applications, the formation of ripples in closed conduits is not well understood, and the problem is still open. This paper presents an experimental study on the formation and migration of sand ripples under a turbulent closed-conduit flow and bed-load conditions. In our experiments, fully-developed turbulent water flows were imposed over a granular bed of known granulometry in a transparent channel, and bed load took place. For different water flow rates and grain diameters, the growth and migration of bedforms were filmed by a high-definition camera, and a numerical code was developed to determine the wavelength and celerity of the bedforms from the acquired images. The obtained results are compared with published stability analyses.
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