集约用海工程对莱州湾水动力环境影响的数值模拟研究

发布时间：2018-10-15 13:34

【摘要】：本文采用非结构化三角网格在综合考虑了大气温度、相对湿度、云量、降雨量、蒸发量和入海径流等因素的基础上首先构建了大尺度渤海三维斜压水动力模型。通过12个潮汐站点、5个潮流站点的实测数据,M2、S2、K1、O1四大分潮的同潮曲线及温盐的时空分布特征对模型进行了验证,结果表明模型能较好地再现渤海水动力及温盐变化过程,可以为后续莱州湾小尺度模型的构建提供水动力及温盐背景场。依托渤海大尺度模型,构建了莱州湾小尺度水动力水质耦合模型并着重对盐度和水质模拟结果进行了分析论证。结果表明夏季莱州湾盐度平面分布的基本规律是自西向东、从湾内向湾外递增,黄河口及小清河口为低值区,北部和东部为高值区。垂向上海区大部呈均匀分布,只是在河口地区,淡水大量输入导致垂向上有一定的盐度梯度。冬季,盐度平面分布格局和夏季保持一致,垂向分布更加趋于均匀,但整体盐度由于降水及河流入海径流的减少较夏季明显偏高。另外,分析得出夏季莱州湾盐度分布的主导因素是黄河径流量,潮流对其影响较弱。05年莱州湾的水质模拟再现了浮游植物典型的双峰分布现象,结合氮磷营养盐的变化过程对该现象的发生机理进行了阐述。依据Redfield数分析了菜州湾营养盐的组成结构,海域整体营养盐水平处于磷限制,但局部海区仍存在氮限制。通过两组数值试验,研究了湾内最重要的两个污染源黄河和小清河对水质的影响,探讨了营养盐的构成比例对浮游植物生长所起的作用：无机磷对浮游植物生长的影响程度要高于无机氮,无机氮的增加也能促进浮游植物含量的升高说明海域整体磷限制作用突出,但是部分海域存在氮限制；小清河点源对莱州湾氮磷无机盐及浮游植物含量水平的影响程度均要弱于黄河。应用模型从潮流场、盐度场、纳潮量和潮通量、水交换能力和营养盐组成五个角度预测了四大集约用海工程的实施给莱州湾水动力及水环境造成的影响。工程对莱州湾全场流场造成的影响有限,影响主要集中在工程附近。由于工程后大潮涨憩时刻高潮位降低,盐水向湾顶的上溯能力减弱,工程后盐度等值线有一定的回退,这在湾内表现尤其明显。落憩时,工程后湾顶潮位回落幅度降低,盐度交换减慢使得湾内盐度等值线后退,低盐区面积增大。填海造陆直接造成的海湾面积减小导致纳潮量和湾口断面潮通量均有不同程度减小。保守物质对流扩散模型表明海湾水体半交换时间较工程前增大45天,增幅达26.9%,海湾水交换能力明显减弱。水体交换不畅使得PO4整体水平升高,DIN含量下降,N/P比普遍降低,海域磷限制作用被削弱。
[Abstract]:In this paper, a large scale baroclinic hydrodynamic model of Bohai Sea is constructed based on unstructured triangular meshes, which take into account the factors of atmospheric temperature, relative humidity, cloud amount, rainfall, evaporation and runoff into the sea. The model is verified by the measured data from 12 tidal stations and 5 tidal stations, the same tide curve of M2S2S2K1O1 and the temporal and spatial distribution characteristics of temperature and salt. The results show that the model can well reproduce the hydrodynamic and thermo-salt variation process in Bohai Sea. It can provide hydrodynamic and temperature-salt background field for the construction of small-scale model in Laizhou Bay. Based on the large scale model of Bohai Sea, the coupling model of small scale hydrodynamic water quality in Laizhou Bay was constructed, and the simulation results of salinity and water quality were analyzed and demonstrated. The results show that the basic law of salinity plane distribution in the Laizhou Bay in summer is from west to east, increasing from the inside of the bay, the estuary of the Yellow River and the mouth of Xiaoqing River is the low value area, and the north and east are the high value areas. Most of the vertical Shanghai area is uniformly distributed, but in the estuarine area, a large amount of fresh water input leads to a certain vertical salinity gradient. In winter, the distribution pattern of salinity plane is consistent with that in summer, and the vertical distribution tends to be more uniform, but the overall salinity is obviously higher than that in summer because of the decrease of precipitation and river runoff into the sea. In addition, the main factor of salinity distribution in Laizhou Bay in summer is the runoff of the Yellow River, and the tidal current has a weak influence on it. The simulation of water quality in Laizhou Bay in 2005 reproduced the typical bimodal distribution of phytoplankton. The mechanism of this phenomenon was explained by the changing process of nitrogen and phosphorus nutrients. According to the Redfield number, the composition of nutrient salt in Caizhou Bay was analyzed. The total nutrient level in the sea area was limited by phosphorus, but there was still nitrogen limitation in the local sea area. The effects of the Yellow River and Xiaoqing River, two of the most important pollution sources in the Bay, on the water quality were studied through two groups of numerical tests. The effect of the proportion of nutrients on phytoplankton growth was discussed: inorganic phosphorus had higher effect on phytoplankton growth than inorganic nitrogen. The increase of inorganic nitrogen also promoted the increase of phytoplankton content. The effect of point source of Xiaoqing River on nitrogen and phosphorus inorganic salt and phytoplankton content in Laizhou Bay was weaker than that in Yellow River. The effects of the four intensive sea projects on the hydrodynamics and water environment of Laizhou Bay were predicted from five aspects: tidal current field, salinity field, tidal capacity and tidal flux, water exchange capacity and nutrient composition. The effect of the project on the whole field of Laizhou Bay is limited, and the effect is mainly near the project. Due to the decrease of high tide level and the abatement of saltwater to the top of the bay after the project, the salinization isoline has a certain retrogression, which is especially obvious in the bay. During the period of falling and resting, the tidal level of the top of the bay decreases after the project, and the salinity exchange slows down, which results in the retrogression of the salinities isoline and the increase of the area of the low salt area in the bay. The decrease of bay area caused by reclamation directly results in the decrease of tidal absorption and tidal flux at the mouth of the bay. The model of conserved material convection and diffusion shows that the half-exchange time of the water body in the bay is increased by 45 days, the increase is 26.9days, and the water exchange capacity of the bay is obviously weakened. The level of PO4 was increased, the content of DIN was decreased, the N / P ratio was generally decreased, and the limiting effect of phosphorus was weakened.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P731.2;P75

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