Granular flow in equilibrium with the bottom: experimental analysis and theoretical prediction
Granular flow in equilibrium with the bottom: experimental analysis and theoretical prediction
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与底部平衡的颗粒流：实验分析和理论预测
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
A. Lamberti
中科院分区：
文献类型：
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作者：
B. Zanuttigh;A. Lamberti
抽象的。本文介绍了在部分充满沙粒的转鼓中以不同速度旋转的颗粒流的测量结果。本文的目的是：提供关于转鼓内颗粒流动的实验证据和测量；比较理论和实验的速度分布；指出理论和实验之间的差异。利用激光多普勒测速仪(LDA)获得了水流中段的速度和“温度”分布，该断面的流动通常是均匀的；还对流动进行了图像分析和目视观测，以评估局部坡度、特征流区的深度和颗粒物质的浓度。给出了一个符合实验速度分布的半经验关系式，并与Takahashi的刚性床和可侵蚀床的速度分布进行了比较。自由表面高度、速度、体积浓度和颗粒尺寸在转鼓上的分布证明，流场的三维特性是不容忽视的。通过提高转鼓转速，对应于临界和超临界流动，观察到了流型的变化，形成了准静态表面波。通过分析实验和理论速度分布的范围和形式，描述了波浪的发展。将实验得到的自由面速度-流量关系与Takahashi侵蚀床模型的自由面速度-流量关系进行了比较，量化并校核了波浪对测量的影响。
Abstract. The paper presents measurements performed on the granular flow that develops in a drum partially filled with sand grains and rotating at various speeds. The aims of the paper are: to provide experimental evidence and measurements on grain flow in a drum; to compare theoretical and experimental velocity profiles; to point out discrepancies among theory and experiments. Velocity and "temperature" profiles were obtained with a Laser Doppler Anemometer (LDA) in the mid-section of the stream, where the flow is usually uniform; image analysis and visual observations of the flow were also carried out to evaluate the local slope, the depths of the characteristic flow regions and the concentration of the granular material. A semi-empirical relation that fits the experimental velocity profiles is presented and compared with Takahashi's velocity distributions for rigid and erodible bed. As proven by the distributions of free surface elevation, velocity, volumetric concentration and grain size across the drum, the three-dimensional nature of the flow field is not negligible. By increasing the drum rotation speed, in correspondence with critical and supercritical flows, changes in the flow regime are observed with formation of quasi-stationary surface waves. Wave development is described by analysing the extension and form of the experimental and theoretical velocity profiles. Wave effects on measurements are quantified and checked comparing the free-surface velocity-discharge relation obtained from experiments and from Takahashi's model for erodible bed.