基于EFDC的大伙房水库水龄和滞留时间的数值模拟研究

发布时间：2018-08-31 09:17

【摘要】：大伙房水库位于中国东北部,是辽宁省重要的的水源地之一,保护水库的水质对于辽宁省的经济发展和社会稳定具有重要的战略意义。大伙房水库属于山区河谷型水库,注入上游的营养物质有可能需要很长的时间才能到达下游区域,这使得营养物质的输运时间对于水体的水质状况有着重要影响。因此深入研究大伙房水库的水动力特征,综合分析不同因素对于大伙房水库输运时间的影响显得尤为重要。本文采用数值模拟的方法对大伙房水库的水动力特征以及输运时间的影响因素进行了研究。本文首先利用基于结构化网格的环境水动力模型EFDC (Environmental Fluid Dynamics Code),综合考虑风、表层热通量以及入库径流,建立了大伙房水库三维水动力模型。通过对比水位和温度的模拟值与实测值对模型进行了验证,验证结果表明建立的水动力模型能够很好地再现水库水位的升降规律和温度的分层一-混合变化过程。然后利用建立的水动力模型,对大伙房水库水体的水龄进行数值模拟研究,综合分析了径流、风、表层热通量及水位变化对于水龄的影响。结果表明径流是影响水龄的主要因素,仅有径流驱动时,在高、平均、低流量下,溢洪道处水体的水龄分别为53.93天、126.96天、458.78天,河道横断面上中间水龄小、两侧水龄大。风对水体输运时间的影响主要通过风生流和风生混合的作用体现出来。同时考虑径流和风的作用时,水龄沿河道横断面的差异减小,在垂向上水龄则是完全均一的。与仅考虑径流时的水龄相比,深水河道处的水龄增加值高于其它河道处水龄的增加值,流量较大时,风对下游水体的水龄影响较大,而流量较小时,风对上游水体的水龄影响较大。表层热通量对输运时间的影响主要通过密度流和温跃层体现出来,当考虑表层热通量的作用时,水龄在局部区域沿水平方向的差异减小,在垂向上呈现表层水龄小、底层水龄大的分层特征,并且越往下游表底层差异越大。表层热通量对表层水体的水龄影响较小,对底层水体的水龄影响较大。水位变化通过改变水体的温度结构从而影响着水体的水龄,水位降低时,水龄整体减小,而且水龄垂向上的差异减小,水位变化对底层和下游水体水龄的影响强于对表层和上游水体水龄的影响。通过已经建立的水动力模型,研究了流量变化对于滞留时间的影响。计算结果表明：在库区河道上,距离大坝越远,滞留时间越大,当地滞留时间越小,而且当地滞留时间和对应区域的滞留时间的差别越大。滞留时间和当地滞留时间随时间的变化服从指数分布,当流量低于平均流量时,滞留时间和当地滞留时间随流量减小而急剧增大。
[Abstract]:Dahuofang Reservoir is located in the northeast of China and is one of the important water sources in Liaoning Province. Protecting the water quality of the reservoir is of great strategic significance to the economic development and social stability of Liaoning Province. Dahuofang Reservoir belongs to the valley type reservoir in mountainous area. It may take a long time for the nutrient injected upstream to reach the downstream area, which makes the transport time of nutrients have an important impact on the water quality. Therefore, it is very important to study the hydrodynamic characteristics of Dahuofang Reservoir and analyze the influence of different factors on the transportation time of Dahuofang Reservoir. In this paper, the hydrodynamic characteristics of Dahuofang Reservoir and the influence factors of transportation time are studied by numerical simulation method. In this paper, a three-dimensional hydrodynamic model of Dahuofang Reservoir is established based on structured grid based environmental hydrodynamic model (EFDC (Environmental Fluid Dynamics Code), considering wind, surface heat flux and inflow runoff. The model is verified by comparing the simulated and measured values of water level and temperature. The results show that the hydrodynamic model can well reproduce the fluctuation law of reservoir water level and the process of stratified and mixed variation of temperature. Then the hydrodynamic model is used to simulate the water age of Dahuofang Reservoir and the effects of runoff wind surface heat flux and water level on water age are analyzed. The results show that runoff is the main factor affecting water age. When runoff is only driven by runoff, the water age at spillway is 53.93 days, 126.96 days and 458.78 days, respectively, under the condition of high, average and low discharge, the middle age of river channel is small, and the water age of both sides is large. The influence of wind on water transport time is mainly reflected by wind-induced flow and wind-induced mixing. At the same time considering the effect of runoff and wind the difference of the cross section along the river channel decreases and the water age is uniform in vertical direction. Compared with the water age when only considering the runoff, the increase value of the water age in the deep water channel is higher than that in the other rivers. When the discharge is larger, the wind has a greater influence on the water age of the downstream water body, but the flow rate is smaller. Wind has a great influence on the water age of upstream water body. The effect of surface heat flux on transport time is mainly reflected by density flow and thermocline. When the effect of surface heat flux is considered, the difference of water age along horizontal direction decreases in local area, and the surface water age is small in vertical direction. The delamination characteristics of the lower water age, and the greater the difference between the bottom layer and the downstream surface. The influence of surface heat flux on water age of surface water is small, and that on water age of bottom water is greater. The variation of water level affects the water age by changing the temperature structure of the water body. When the water level decreases, the water age decreases as a whole, and the vertical difference of water age decreases. The influence of water level change on water age of bottom and downstream water is stronger than that on surface and upstream water age. Based on the established hydrodynamic model, the effect of flow rate change on residence time is studied. The calculation results show that the farther away from the dam, the larger the detention time, the smaller the local detention time, and the greater the difference between the local detention time and the corresponding region. When the flow rate is lower than the average flow rate, the residence time and the local residence time increase sharply with the decrease of the flow rate.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV697

【参考文献】