Longitudinal dispersion in sewer pipes with sediments

Data from the laboratory experiments, studying the longitudinal dispersion in a pipe with sediments, simulating the real conditions in a sewer pipe.
Experiments were performed in a laboratory flume with circular cross-section. In aim to simulate the real hydraulic condition in sewer pipe, sand with fraction 0.6-1.2 mm was placed on the bottom of the pipe. In total, 23 experiments, with 4 different layer thickness were performed: layer thickness of 0 mm (no sediments), 8.5 mm (3.4% of the pipe diameter), 25 mm (10%) and 35 mm (14%). For each thickness of the sediment layer a set of tracer experiment with different discharges was performed. The discharge ranges were from 0.14 up 2.5 l.s-1, this corresponds to the range of Reynolds number 500-18 000. The inner diameter of the pipe was 250 mm, length was 12 m, slope of the pipe was 5 ‰. Material of the pipe was smooth transparent plastic.

Results of the tracer experiments show, that the value of the longitudinal dispersion coefficient Dx in the hydraulic conditions of circular sewer pipe with sediment and deposits decreases almost linearly to a certain limit (inflexion point), which is individual for each particular sediment thickness. Below this limit the value of the dispersion coefficient starts to rise again, together with increasing asymmetricity of the concentration time course, caused by transient (dead) storage zones.

本数据集源自于实验室实验，旨在研究沉积物在管道中的纵向扩散现象，并模拟下水道管道中的实际工况。实验于圆形横截面的实验室水槽中进行。为了模拟下水道管道中的实际水力条件，于管道底部铺设了粒径介于0.6至1.2毫米之间的沙粒。共计进行了23次实验，分别对应4种不同的层厚：0毫米（无沉积物）、8.5毫米（管道直径的3.4%）、25毫米（10%）以及35毫米（14%）。针对每种沉积物层厚，均进行了一系列不同排放量的示踪实验。排放量范围从0.14升至2.5升/秒，对应雷诺数的范围为500至18,000。管道内径为250毫米，长度为12米，管道坡度为5‰。管道材料为光滑透明的塑料。示踪实验结果显示，在含有沉积物和沉积物的圆形下水道管道水力条件下，纵向扩散系数Dx的值几乎呈线性下降至某一特定极限（拐点），该拐点因每种特定的沉积物厚度而异。在此极限以下，扩散系数的值开始再次上升，同时，由于瞬时（死区）储存区的存在，浓度时间过程的不对称性也随之增加。