基于随机游动模型的铁山港水交换的数值模拟

Numerical Simulation on Water Exchange in Tieshan Bay Based on a Random Walk Model

采用三维浅海水动力模型和粒子随机游动模型,模拟了铁山港潮汐、潮流场,分析了湾内水体平均驻留时间的时空特征和物质迁移特征.研究结果表明,铁山港海水交换主要受潮汐控制,上层海水与湾外水交换率大,平均驻留时间为9.84d,下层海水为25.18d;腹大口小的海湾内湾顶水交换较慢,湾口和湾中水交换较快;落潮期水体交换速度明显快于涨潮期.采用单点中性粒子追踪公馆河入海处等5个较典型位置水体的运动轨迹,结果表明北暮—营盘附近口门海域和石头埠沿岸水交换活跃,利于水体物理自净扩散;湾顶、白沙河和沙田均水交换缓慢,容易造成物质的沿岸堆积.

The tides and tidal currents in Tieshan Bay were simulated with a three-dimensional hydrodynamic model together with a random walk particle-tracking model.The temporal and spatial distribution characteristics of mean residence time and transportation of substances in Tieshan Bay were analyzed as well.The structure of the tidal currents was revealed to play a decisive role in water exchange in Tieshan Bay.Higher exchange rate was shown in the upper layer.The mean residence time was 9.84 dfor the upper layer,and 25.18 dfor the bottom layer.The capability of water exchange decreased significantly from mouth to top of the bay and was distinctly higher in the low-flow periods than that in the high-flow periods.Single neutral particle undergoing advection-dispersion was introduced at five typical locations in the flow model,and the path lines were simulated.Resulting from a single particle tracking run,the water exchange was faster in the area of Beimu-Yingpan and Shitoubu,which could be conducive to the physical self-purification.Moreover,the water exchange was slower in the top of the bay,as well as Baisha river and Shatian,leading to substances accumulated along the coast easily.