中文摘要：

为研究U形渠道圆头量水柱的测流规律及影响因素，基于绕流理论和RNGk-ε湍流模型，对18种体型圆头量水柱5种工况下的水力性能进行全流场数值计算，获得了时均流场、断面流速分布及柱后水流流态，并与实测值进行对比。同时，通过模型试验与数值仿真研究了V形尾翼对测流的影响。结果表明：水力参数的实测值与模拟值具有较好的一致性，渠道底坡为1/1000，流量为45.01L/s，收缩比及长宽比分别为0.50和2时，驻点处横断面最大流速模拟值与实测值相对误差为1.51%，水深15cm位置剖面最大流速模拟值与实测值相对误差为0.45%。适宜长宽比的V形尾翼可以有效改善过槽水流：当收缩比为0.50～0.75时，建议长宽比为3/2～2；当收缩比＜0.50时，长宽比应相应增大，但不宜＞5/2。通过回归分析得到的圆头量水柱流量计算公式，在收缩比为0.63时最大测流误差为4.95%，平均误差仅为0.10%，该研究为圆头量水柱在中国北方灌区末级渠系的进一步应用提供参考。

英文摘要：

In this paper, water-measuring column with a round head was proposed to measure flow based on the cylindrical flow around theory. In the column, the cylindrical flume was improved by adding a V-shaped empennage behind it to reduce head loss, improve the accuracy of flow measurement and increase sediment transport capacity. The water-measuring column with a round head was installed vertically in a U-shaped channel and its symmetry plane was overlapped with the centerline of the channel bottom. By controlling the length of the V-shaped empennage, it could make the flow pattern steady and reduce head loss. Based on the cylindrical flow around theory and RNG k-εturbulence model, hydraulic performance of the whole flow field of water-measuring column with a round head in 18 somatotypes under 5 working conditions were numerically calculated. And we obtained the time-averaged flow field, sectional velocity distribution, flow pattern behind the column as well as the measured values and the simulated values of the related hydraulic parameters. The comparison of simulated and measured hydraulic parameters values showed that they had good consistency. When the channel slope was 1/1000, discharge was 0.045m3/s, the contraction ratio was 0.50, and the aspect ratio was 2, the relative error of the maximum velocity of cross-section at a stagnation point between the simulated value and the measured value was 1.51%, and the relative error of the maximum velocity in a profile at 15 cm upward to water surface between the simulated value and the measured value was 0.45%. Therefore, simulation results can provide valuable information for rational design of a water-measuring column with a round head and its analysis of flow field measurements. On the one hand, an oversized contraction ratio may cause excessive upstream backwater and affect the normal operation of the channel. On the other hand, it was difficult to form a critical flow if the contraction ratio was too small. Based on the experimental data, a suitable range of contract