大潮差河口闸下水流的流动特性分析

福建数座河口水闸发生剧烈淘刷,闸上游和下游的最大冲刷深度达到闸室高度的0.5~1.2倍,且屡修屡毁。有的水闸经多次除险加固后,不得不再花巨资重建。通过数学模型和物理模型揭示了河口水闸下游水位因受东海大潮差海潮影响发生剧烈波动时的变化规律,发现了水闸泄流过程中的间歇性淹没及非常工况甚至出现逆流的独特流动现象,给出了典型日孔流及堰流泄流能力动态变化过程线,分析了消能工变化对闸址水流结构的显著影响,并对水闸水毁修复前后闸下冲刷进行了预测。结果表明:水闸修复前闸下涨急最高水位4.53 m,修复后下降0.67 m,水闸修复后逆流现象减弱。修复后首次水跃位置往上游移动了35 m,平均水跃高度下降47.46%,闸后及二级池末端最大流速2.27 m/s和0.08 m/s,较修复前分别下降了40.58%和96.48%。常遇泄流条件下,水闸的淹没度和泄流能力呈现不断变化的动态过程。当西溪水闸62#先启孔全开,上游保持正常高水位3.2 m,下游为最低潮位-0.72 m时,修复后最大冲刷深度减少64.48%,消能防冲效果十分明显。研究成果对河口水闸安全运行具有一定的参考价值。

Flow phenomena and main characteristics under estuary with large tidal range

Serious scours occur at several estuary sluices in Fujian Province，for which the maximum upstream and downstream scouring depths of the sluices reach to 0.5~1.2 times of the heights of the sluice chambers，even frequent restorations are followed by frequent failures. For some sluices，huge sums of money have to be reinvested to reconstruct them after the risk elimination and reinforcement made for them for many times. Through the relevant mathematical model and physical model，the changing law of the downstream water level of estuary sluice during the severe fluctuation caused by the effect of the tide with large tidal range from the East China Sea is revealed and the intermittent submergence，abnormal operation condition and even the unusual flow phenomenon of counter flow during the discharge of sluice are found out； from which the hydrographs of the dynamic changes of the discharging capacities of the typical daily orifice flow and weir flow are given out，and then the significant impact from the change of energy dissipator on the flow structure at the sluice site is analyzed，while the scours in front of and behind of sluice before and after the restoration of it are predicted as well. The result shows that before restoration of sluice, the maximum water level rapidly risen is 4.53 m, which is lowered by 0.67 m after restoration, thus the phenomenon of counter flow is accordingly weakened. The initial hydraulic jump after restoration moves upstream by 35 m, while the average height of the hydraulic jump is decreased by 47.46%, and then the maximum flow rates are 2.27 m/s and 0.08 m/s behind sluice and at the end of the second stage stilling pool respectively, which are decreased by 40.58% and 96.48% respectively, if compared with those before restoration.Under the normal discharging condition，both the submergence and the discharging capacity present the dynamic processes of continuous changes. When the No.62 first opening outlet of Xixi Sluic is fully opened，the upstream water level maintains at the normal high level of 3.2 m and the downstream water level is at the lowest tidal level of -0.72 m，the maximum scouring depth after the restoration is reduced by 64.48% with a significant energy dissipation and anti scouring effect. The study result has a certain reference for the safety operation of estuary sluice.