Urban runoff (re)mobilises solids present on the street surface and transport them to urban drainage systems. The solids reduce the hydraulic capacity of the drainage system due to sedimentation and on the quality of receiving water bodies due to discharges via outfalls and combined sewer overflows (CSOs) of solids and associated pollutants. To reduce these impacts, gully pots, the entry points of the drainage system, are typically equipped with a sand trap, which acts as a small settling tank to remove suspended solids. This study presents data obtained using Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) measurements in a scale 1:1 gully to quantify the relation between parameters such as the gully pot geometry, discharge, sand trap depth, and sediment bed level on the flow field and subsequently the settling and erosion processes. The results show that the dynamics of the morphology of the sediment bed influences the flow pattern and the removal efficiency in a significant manner, prohibiting the conceptualization of a gully pot as a completely mixed reactor. Resuspension is initiated by the combination of both high turbulent fluctuations and high mean flow, which is present when a substantial bed level is present. In case of low bed levels, the overlaying water protects the sediment bed from erosion.

中文翻译：

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沟渠中沉积物形态与流速场的实验研究

城市径流（重新）流动存在于街道表面的固体并将它们输送到城市排水系统。固体会因沉淀而降低排水系统的水力容量，以及因固体和相关污染物通过排污口和合流下水道溢流 (CSO) 排放而降低接收水体质量。为了减少这些影响，排水系统的入口点沟渠通常配备一个沙坑，作为一个小的沉淀池来去除悬浮固体。本研究提供了使用粒子图像测速 (PIV) 和激光多普勒风速测量 (LDA) 测量获得的数据，在比例为 1:1 的沟渠中量化参数之间的关系，例如沟渠几何形状、流量、沙坑深度、流场上的沉积物床水平以及随后的沉降和侵蚀过程。结果表明，沉积物床形态的动力学以显着的方式影响流型和去除效率，阻碍了将沟渠作为完全混合反应器的概念化。再悬浮是由高湍流波动和高平均流量的组合引发的，当存在相当大的床位时就会出现这种情况。在低床位的情况下，上覆水保护沉积床免受侵蚀。再悬浮是由高湍流波动和高平均流量的组合引发的，当存在相当大的床位时就会出现这种情况。在低床位的情况下，上覆水保护沉积床免受侵蚀。再悬浮是由高湍流波动和高平均流量的组合引发的，当存在相当大的床位时就会出现这种情况。在低床位的情况下，上覆水保护沉积床免受侵蚀。