This experimental study investigates the cause of nonuniform invert abrasion observed at sediment bypass tunnel (SBT) bends by examining the variations in velocity distributions, turbulence properties, bed shear stress, and bulk sediment movements under three supercritical bend flow conditions, detailed investigation of such flow is scarce. Using a laboratory-scaled model (1:22) of the downstream bend at Solis SBT, Switzerland, the research utilized particle tracking velocimetry and high-speed cameras with spherical sandstones and glass spheres representing sediments. The results indicate that as the secondary currents develop in the flow direction, the flow properties and sediments redistribute across the channel: the high-momentum fluids are directed toward the outer wall, the bed shear stress increases toward the outer wall, and the sediments are pushed toward the inner wall, which then follow this path downstream, even in straight sections, despite lower bed shear stress. This distribution of sediments, driven by secondary currents, leads to deeper invert abrasions toward the inner wall at SBT bends and downstream sections. Thus, these abrasions are primarily influenced by sediment movement rather than the bed shear stress alone. The study's findings are also valuable for validating future numerical simulations.

中文翻译：

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使用 PTV 和视频片段研究窄通道弯道中沉积物颗粒的超临界流特性和运动


本实验研究通过检查三种超临界弯曲流条件下的速度分布、湍流特性、床剪切应力和大量沉积物运动的变化，调查了在沉积物旁路隧道 （SBT） 弯头观察到的非均匀内倾磨损的原因，对这种流动的详细研究很少。该研究使用瑞士 Solis SBT 下游弯道的实验室比例模型 （1：22），利用粒子跟踪测速仪和高速相机，使用代表沉积物的球形砂岩和玻璃球。结果表明，随着次级流沿流向发展，流动特性和沉积物在通道中重新分布：高动量流体被引导至外壁，床面剪切应力向外壁增加，沉积物被推向内壁，然后内壁沿着这条路径向下游移动，即使是笔直的截面， 尽管床层剪切应力较低。这种由次级流驱动的沉积物分布导致在 SBT 弯曲和下游部分向内壁方向的更深的内反转磨损。因此，这些擦伤主要受沉积物运动的影响，而不仅仅是河床剪切应力的影响。该研究的结果对于验证未来的数值模拟也很有价值。