广西北海银滩海域实测海流特征和悬沙输运分析

Current characteristic and suspended sediment transport in the Silver Beachoffshore region,Beihai,Guangxi

基于广西北海银滩近岸海域2012年和2013年两次大小潮过程的实测流速和悬沙资料,对银滩附近海域潮流特征、运动形态、余流分布、悬沙输运机制进行了分析和讨论,对该海域的水动力状况及悬沙输运有了更进一步了解,为北海银滩的保护与规划提供了科学依据。结果显示:涨潮期间实测最大流速为44cm·s^-1,落潮期间最大流速为105cm·s^-1;而计算所得潮流最大可能流速为70.2cm·s^-1,表明实测流速中非潮流作用显著。各主要分潮流基本以O1和K1及M2为主,潮流运动形式以往复流为主,部分测站呈现出旋转流性质,与岸线或港湾水道走向基本一致。余流受北部湾北部环流及风的影响,以西北向为主,表层余流流速明显大于底层,余流最大可达25.5cm·s^-1。观测期间悬沙颗粒基本为粉砂,悬沙输运以平流输运主导,其次为潮泵效应和剪切效应。沿岸输沙和风浪掀沙可能对该海域悬沙输运有较大影响。

Based on the measured current and suspended sedimentdata on spring and neap tides in the Silver Beach offshore region,Beihai,Guangxi,in 2012and 2013,the current characteristics and suspended sediment transport mechanism in the offshore are analyzed and discussed.This study will provide an important scientific support for the protection and planning of the Silver Beach in Beihai.Results show that the observed maximum flood current speed is 44cm·s-1,and the maximum ebb current speed is 105cm·s-1.However,the calculated maximum probable current speed is only 70.2cm·s-1,indicating the importance of the non-tidal flow in this region.The O1,K1and M2are leaded in the tidal current andthe last two are mainly rectilinear.The residual current is mainly northwestward due to the influence of the circulation in the northern Gulf of the Tonkin.The surface residual current is stronger than that at the bottom.The maximum residual current can reach up to 25.5cm·s-1.The net suspended-sediment transport is dominated by the advection term,followed by tidal pumping and shear effect.Coastal sediment transport and wind waves may have a great impact on suspended sediment transport in this area.