丁坝头部附近速度分布特征及对通航影响距离的试验研究

Experimental studies on flow characteristics near spur dike head and the influence on navigation distance

河道中修建丁坝将改变丁坝附近的水流流态,形成复杂的三维水流,可能影响坝头附近的船舶通航安全。为研究丁坝断面的三维流速分布、坝头附近的流态特征以及丁坝存在对通航的影响范围等问题,在概化模型水槽中进行试验研究,利用多普勒测速仪对丁坝断面流速进行测量,分析丁坝断面三维流速分布资料,发现距离丁坝头部一定范围处,丁坝断面横向流速的变化率趋近于0,并以此范围作为丁坝对水流运动及通航的影响距离。通过对不同影响因素的分析,得到丁坝对通航影响距离与随弗汝德数、压缩比等参数的相关关系式。

Construction of spur dikes in rivers makes variation to the flow pattern in the cross section of the spur dikes. The complex three- dimensional flow is generated, and it will affect the ship navigation safety near the spur dike head. Owing to equipment limitations, the research on velocity distribution of spur dike section is inadequate. The research on the influenced distances of water movement and navi- gation due to the existence of the spur dikes is seldom found. With the development of Doppler technology and improvement of testing in- struments, some problems such as three-dimensional velocity distribu- tion of spur dike section and tile fluid state near the spur dike head could be realized. For this propose, experiments are carried out in the generalized model flume where Doppler Yectrino is utilized to measure and analyze the velocity distribution of spur dike section. From the detailed analysis, the mechanism of longitudinal velocity distribution formation and the relationship between vertical velocity distribution and vortex of the spur dike head is well explained. The most significant finding is the change rate of the lateral velocity at the spur dike section tends to zero in the certain distance scope near the spur dike bead. It is considered as the influential distance of the spur dike to the navigation. Finally, through analyzing various affecting factors, the relationships of influenced navigation distances with Froude number and compression ratio are obtained. The calculated relationship has provided a method to determine the navigation safety distance in waterway regulation project.