潮汐汊道均衡断面面积计算与稳定性分析中的问题 ——以海南陵水新村为例

通过对潮汐汊道稳定性与均衡断面面积定义的探讨,明确了O Brien等、Kreeke与Bruun对潮汐汊道稳定性定义的差异。通过不同方法求解一维水力学与连续方程,计算了海南陵水新村潮汐汊道的封闭曲线,并采用华南沿海A-P关系得出的均衡流速曲线及Soulsby临界流速曲线,计算了新村潮汐汊道的均衡断面面积,根据O Brien等与Kreeke的稳定性定义对新村潮汐汊道的稳定性进行了判别。结果表明,在大、小潮期用不同方法及不同的断面变化方式得出的稳定均衡断面面积(A2)在同样的均衡流速曲线下基本一致,而小潮期的稳定均衡断面面积要小于大潮期,最大流速处的断面面积(Acc)要大于大潮期。A2、Acc及饱满系数为0.8时对应的断面面积三者之间具有较大的差异。用封闭曲线求取潮汐汊道均衡断面面积并进行稳定性判断,在概念上有一定意义,可以作为潮汐汊道稳定性判断的一个依据,但通过求解一维水力学与连续方程以获取均衡断面面积则具有较大的局限性与不确定性。应通过中长期的野外观测、数值模拟与物理模型,以确定潮汐汊道的水动力特征以及地形演变规律,得出A-P关系进而求出均衡断面面积,并结合Bruun方法判定潮汐汊道的稳定性。

Stability analysis and equilibrium area calculation of tidal inlet——A case study in Xincun inlet, Linshui, Hainan Island

The definitions of stability and equilibrium area of tidal inlets were discussed firstly to clarify the differences among those by O'Brien et al,Kreeke,and Bruun.The closure curve was obtained by different methods through solving one-dimentional hydraulics and continuity equation,together with the equilibrium velocity obtained by Zhang's A-P relationship and the Soulsby's critical velocity,the equilibrium area was calculted and the stability of the inlet was discussed.The results showed that the stable equilibrium areas(A_2) during spring and neap tides obtained by using different methods and under the same equilibrium velocity curve were similar although it was smaller during neap tide than during spring tide,and the area corresponding to the maximum velocity(A_cc) during neap tide was relatively larger than that during spring tide.The A_2,A_cc and the area for K equal to 0.8 were significantly different for both periods.Though the closure curve method is basically of some theoretical importance,it has minor application in defining equilibrium area by solving one-dimentional hydraulics and continuity edquation due to its large uncertainty and variability.The equilibrium area and the stability of an inlet should be determined through medium-to-long-term observation and numerical modeling,and combined with the Bruun's Rule.