人工采砂坑对规则波岸礁水动力特性的影响研究

Study on the effects of artificial excavation pits on the hydrodynamic characteristics of regular wave over fringing reef

本文基于非静压单相流模型NHWAVE,系统分析了人工采砂坑对规则波岸礁水动力特性的影响。研究结果表明:人工采砂坑会使局部波高在坑前和坑内分别增大和减小,但是采砂坑对礁缘和礁后岸滩附近局部波高的变化无显著影响;采砂坑对平均水位的变化几乎没有影响。随着入射波高的增大,采砂坑附近局部波高的变化幅度相对减小,但礁坪上波浪增水随之增大。礁坪水深越大,采砂坑附近的局部波高变化幅度越大,但礁坪上的增水效应会随着礁坪水深的增大而减小。当波浪周期增大时,波高在坑前升高、坑内降低这一现象更为显著,小周期的波浪几乎不发生这种现象。人工采砂坑的位置、宽度和深度对规则波的传播变形均有显著影响;采砂坑从礁缘移动至岸线附近过程中,波高在坑前升高和坑内降低现象逐渐不明显,但岸线附近的平均水位逐渐增大;随着采砂坑宽度和深度的增大,岸线附近的平均水位逐渐减小。采砂坑的存在在一定程度上会增加波浪的反射系数;采砂坑的存在显著降低了波浪在岸线附近的爬高。研究结果可进一步为评估珊瑚礁上的采砂活动提供参考依据。

Based on the nonhydrostatic single-phase flow numerical wave model(NHWAVE),this paper systematically analyses the effects of artificial extraction pits on the hydrodynamic characteristics of regular wave fringing reefs.The results show that the artificial excavation pits increase and decrease the local wave height in front of and inside the pits respectively,but the pits have no significant effect on the change of local wave height near the reef edge and the shoreline behind the reef.excavation pits had little effect on the change in mean water level.As the incident wave height increases,the magnitude of the change in local wave height near the excavation pit decreases relatively,but the wave setup increases with it.The greater the water depth on reef flat,the greater the amplitude of change in local wave height near the excavation pit,but the effect of wave setup on the reef decreases as the water depth on reef flat increases.As the wave period increases,the phenomenon of wave height increasing in front of the pit and decreasing in the pit is more pronounced;this phenomenon hardly occurs for small wave periods.The location,width and depth of the artificial excavation pits have a significant effect on the evolution of the propagation deformation of regular waves;as the pits move from the reef edge to near the shoreline,the phenomenon of wave height increasing in front of the pits and decreasing inside the pits gradually becomes less pronounced,but the mean water level near the shoreline gradually increases;as the width and depth of the pits increase,the mean water level near the shoreline gradually decreases.The presence of excavation pits increases the wave reflection coefficient to some extent;the presence of excavation pits significantly reduces the wave runup near the shoreline.The results of the study may provide a further reference for assessing sand mining activities on coral reefs.